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<div class="section" id="header-data-units">
<h1>Header Data Units<a class="headerlink" href="#header-data-units" title="Permalink to this headline">¶</a></h1>
<p>The <a class="reference internal" href="images.html#astropy.io.fits.ImageHDU" title="astropy.io.fits.ImageHDU"><tt class="xref py py-class docutils literal"><span class="pre">ImageHDU</span></tt></a> and <a class="reference internal" href="images.html#astropy.io.fits.CompImageHDU" title="astropy.io.fits.CompImageHDU"><tt class="xref py py-class docutils literal"><span class="pre">CompImageHDU</span></tt></a> classes are discussed in the
section on <a class="reference internal" href="images.html#images"><em>Images</em></a>.</p>
<p>The <a class="reference internal" href="tables.html#astropy.io.fits.TableHDU" title="astropy.io.fits.TableHDU"><tt class="xref py py-class docutils literal"><span class="pre">TableHDU</span></tt></a> and <a class="reference internal" href="tables.html#astropy.io.fits.BinTableHDU" title="astropy.io.fits.BinTableHDU"><tt class="xref py py-class docutils literal"><span class="pre">BinTableHDU</span></tt></a> classes are discussed in the
section on <a class="reference internal" href="tables.html#tables"><em>Tables</em></a>.</p>
<div class="section" id="primaryhdu">
<h2><a class="reference internal" href="#astropy.io.fits.PrimaryHDU" title="astropy.io.fits.PrimaryHDU"><tt class="xref py py-class docutils literal"><span class="pre">PrimaryHDU</span></tt></a><a class="headerlink" href="#primaryhdu" title="Permalink to this headline">¶</a></h2>
<dl class="class">
<dt id="astropy.io.fits.PrimaryHDU">
<em class="property">class </em><tt class="descclassname">astropy.io.fits.</tt><tt class="descname">PrimaryHDU</tt><big>(</big><em>data=None</em>, <em>header=None</em>, <em>do_not_scale_image_data=False</em>, <em>uint=False</em>, <em>scale_back=False</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L755" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.PrimaryHDU" title="Permalink to this definition">¶</a></dt>
<dd><p>Bases: <tt class="xref py py-class docutils literal"><span class="pre">astropy.io.fits.hdu.image._ImageBaseHDU</span></tt></p>
<p>FITS primary HDU class.</p>
<dl class="method">
<dt id="astropy.io.fits.PrimaryHDU.add_checksum">
<tt class="descname">add_checksum</tt><big>(</big><em>when=None</em>, <em>override_datasum=False</em>, <em>blocking='standard'</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L1099" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.PrimaryHDU.add_checksum" title="Permalink to this definition">¶</a></dt>
<dd><p>Add the <tt class="docutils literal"><span class="pre">CHECKSUM</span></tt> and <tt class="docutils literal"><span class="pre">DATASUM</span></tt> cards to this HDU with
the values set to the checksum calculated for the HDU and the
data respectively. The addition of the <tt class="docutils literal"><span class="pre">DATASUM</span></tt> card may
be overridden.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>when</strong> : str, optional</p>
<blockquote>
<div><p>comment string for the cards; by default the comments
will represent the time when the checksum was calculated</p>
</div></blockquote>
<p><strong>override_datasum</strong> : bool, optional</p>
<blockquote>
<div><p>add the <tt class="docutils literal"><span class="pre">CHECKSUM</span></tt> card only</p>
</div></blockquote>
<p><strong>blocking: str, optional</strong> :</p>
<blockquote class="last">
<div><p>“standard” or “nonstandard”, compute sum 2880 bytes at a time, or
not</p>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
<p class="rubric">Notes</p>
<p>For testing purposes, first call <a class="reference internal" href="#astropy.io.fits.PrimaryHDU.add_datasum" title="astropy.io.fits.PrimaryHDU.add_datasum"><tt class="xref py py-obj docutils literal"><span class="pre">add_datasum</span></tt></a> with a <tt class="xref py py-obj docutils literal"><span class="pre">when</span></tt>
argument, then call <a class="reference internal" href="#astropy.io.fits.PrimaryHDU.add_checksum" title="astropy.io.fits.PrimaryHDU.add_checksum"><tt class="xref py py-obj docutils literal"><span class="pre">add_checksum</span></tt></a> with a <tt class="xref py py-obj docutils literal"><span class="pre">when</span></tt> argument and
<tt class="xref py py-obj docutils literal"><span class="pre">override_datasum</span></tt> set to <tt class="xref py py-obj docutils literal"><span class="pre">True</span></tt>. This will provide
consistent comments for both cards and enable the generation
of a <tt class="docutils literal"><span class="pre">CHECKSUM</span></tt> card with a consistent value.</p>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.PrimaryHDU.add_datasum">
<tt class="descname">add_datasum</tt><big>(</big><em>when=None</em>, <em>blocking='standard'</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L1063" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.PrimaryHDU.add_datasum" title="Permalink to this definition">¶</a></dt>
<dd><p>Add the <tt class="docutils literal"><span class="pre">DATASUM</span></tt> card to this HDU with the value set to the
checksum calculated for the data.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>when</strong> : str, optional</p>
<blockquote>
<div><p>Comment string for the card that by default represents the
time when the checksum was calculated</p>
</div></blockquote>
<p><strong>blocking: str, optional</strong> :</p>
<blockquote>
<div><p>“standard” or “nonstandard”, compute sum 2880 bytes at a time, or
not</p>
</div></blockquote>
</td>
</tr>
<tr class="field-even field"><th class="field-name">Returns :</th><td class="field-body"><p class="first"><strong>checksum</strong> : int</p>
<blockquote class="last">
<div><p>The calculated datasum</p>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
<p class="rubric">Notes</p>
<p>For testing purposes, provide a <tt class="xref py py-obj docutils literal"><span class="pre">when</span></tt> argument to enable the
comment value in the card to remain consistent. This will
enable the generation of a <tt class="docutils literal"><span class="pre">CHECKSUM</span></tt> card with a consistent
value.</p>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.PrimaryHDU.copy">
<tt class="descname">copy</tt><big>(</big><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L819" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.PrimaryHDU.copy" title="Permalink to this definition">¶</a></dt>
<dd><p>Make a copy of the HDU, both header and data are copied.</p>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.PrimaryHDU.filebytes">
<tt class="descname">filebytes</tt><big>(</big><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L761" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.PrimaryHDU.filebytes" title="Permalink to this definition">¶</a></dt>
<dd><p>Calculates and returns the number of bytes that this HDU will write to
a file.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><strong>None</strong> :</td>
</tr>
<tr class="field-even field"><th class="field-name">Returns :</th><td class="field-body"><strong>Number of bytes</strong> :</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.PrimaryHDU.fileinfo">
<tt class="descname">fileinfo</tt><big>(</big><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L779" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.PrimaryHDU.fileinfo" title="Permalink to this definition">¶</a></dt>
<dd><p>Returns a dictionary detailing information about the locations
of this HDU within any associated file. The values are only
valid after a read or write of the associated file with no
intervening changes to the <a class="reference internal" href="hdulists.html#astropy.io.fits.HDUList" title="astropy.io.fits.HDUList"><tt class="xref py py-obj docutils literal"><span class="pre">HDUList</span></tt></a>.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>None</strong> :</p>
</td>
</tr>
<tr class="field-even field"><th class="field-name">Returns :</th><td class="field-body"><p class="first"><strong>dictionary or None</strong> :</p>
<blockquote class="last">
<div><p>The dictionary details information about the locations of
this HDU within an associated file. Returns <tt class="xref py py-obj docutils literal"><span class="pre">None</span></tt> when
the HDU is not associated with a file.</p>
<p>Dictionary contents:</p>
<table border="1" class="docutils">
<colgroup>
<col width="15%" />
<col width="85%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Key</th>
<th class="head">Value</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td>file</td>
<td>File object associated with the HDU</td>
</tr>
<tr class="row-odd"><td>filemode</td>
<td>Mode in which the file was opened (readonly, copyonwrite,
update, append, ostream)</td>
</tr>
<tr class="row-even"><td>hdrLoc</td>
<td>Starting byte location of header in file</td>
</tr>
<tr class="row-odd"><td>datLoc</td>
<td>Starting byte location of data block in file</td>
</tr>
<tr class="row-even"><td>datSpan</td>
<td>Data size including padding</td>
</tr>
</tbody>
</table>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="classmethod">
<dt id="astropy.io.fits.PrimaryHDU.fromstring">
<em class="property">classmethod </em><tt class="descname">fromstring</tt><big>(</big><em>data</em>, <em>fileobj=None</em>, <em>offset=0</em>, <em>checksum=False</em>, <em>ignore_missing_end=False</em>, <em>**kwargs</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L166" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.PrimaryHDU.fromstring" title="Permalink to this definition">¶</a></dt>
<dd><p>Creates a new HDU object of the appropriate type from a string
containing the HDU’s entire header and, optionally, its data.</p>
<p>Note: When creating a new HDU from a string without a backing file
object, the data of that HDU may be read-only. It depends on whether
the underlying string was an immutable Python str/bytes object, or some
kind of read-write memory buffer such as a <tt class="xref py py-obj docutils literal"><span class="pre">memoryview</span></tt>.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>data</strong> : str, bytearray, memoryview, ndarray</p>
<blockquote>
<div><p>A byte string contining the HDU’s header and, optionally, its data.
If <tt class="xref py py-obj docutils literal"><span class="pre">fileobj</span></tt> is not specified, and the length of <tt class="xref py py-obj docutils literal"><span class="pre">data</span></tt> extends
beyond the header, then the trailing data is taken to be the HDU’s
data. If <tt class="xref py py-obj docutils literal"><span class="pre">fileobj</span></tt> is specified then the trailing data is ignored.</p>
</div></blockquote>
<p><strong>fileobj</strong> : file (optional)</p>
<blockquote>
<div><p>The file-like object that this HDU was read from.</p>
</div></blockquote>
<p><strong>offset</strong> : int (optional)</p>
<blockquote>
<div><p>If <tt class="xref py py-obj docutils literal"><span class="pre">fileobj</span></tt> is specified, the offset into the file-like object at
which this HDU begins.</p>
</div></blockquote>
<p><strong>checksum</strong> : bool (optional)</p>
<blockquote>
<div><p>Check the HDU’s checksum and/or datasum.</p>
</div></blockquote>
<p><strong>ignore_missing_end</strong> : bool (optional)</p>
<blockquote>
<div><p>Ignore a missing end card in the header data. Note that without
the end card the end of the header can’t be found, so the entire
data is just assumed to be the header.</p>
</div></blockquote>
<p><strong>kwargs</strong> : (optional)</p>
<blockquote class="last">
<div><p>May contain additional keyword arguments specific to an HDU type.
Any unrecognized kwargs are simply ignored.</p>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="classmethod">
<dt id="astropy.io.fits.PrimaryHDU.readfrom">
<em class="property">classmethod </em><tt class="descname">readfrom</tt><big>(</big><em>fileobj</em>, <em>checksum=False</em>, <em>ignore_missing_end=False</em>, <em>**kwargs</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L282" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.PrimaryHDU.readfrom" title="Permalink to this definition">¶</a></dt>
<dd><p>Read the HDU from a file. Normally an HDU should be opened with
<tt class="xref py py-obj docutils literal"><span class="pre">fitsopen()</span></tt> which reads the entire HDU list in a FITS file. But this
method is still provided for symmetry with <a class="reference internal" href="files.html#astropy.io.fits.writeto" title="astropy.io.fits.writeto"><tt class="xref py py-obj docutils literal"><span class="pre">writeto()</span></tt></a>.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>fileobj</strong> : file object or file-like object</p>
<blockquote>
<div><p>Input FITS file. The file’s seek pointer is assumed to be at the
beginning of the HDU.</p>
</div></blockquote>
<p><strong>checksum</strong> : bool</p>
<blockquote>
<div><p>If <tt class="xref py py-obj docutils literal"><span class="pre">True</span></tt>, verifies that both <tt class="docutils literal"><span class="pre">DATASUM</span></tt> and
<tt class="docutils literal"><span class="pre">CHECKSUM</span></tt> card values (when present in the HDU header)
match the header and data of all HDU’s in the file.</p>
</div></blockquote>
<p><strong>ignore_missing_end</strong> : bool</p>
<blockquote class="last">
<div><p>Do not issue an exception when opening a file that is
missing an <tt class="docutils literal"><span class="pre">END</span></tt> card in the last header.</p>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.PrimaryHDU.req_cards">
<tt class="descname">req_cards</tt><big>(</big><em>keyword</em>, <em>pos</em>, <em>test</em>, <em>fix_value</em>, <em>option</em>, <em>errlist</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L985" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.PrimaryHDU.req_cards" title="Permalink to this definition">¶</a></dt>
<dd><p>Check the existence, location, and value of a required <a class="reference internal" href="cards.html#astropy.io.fits.Card" title="astropy.io.fits.Card"><tt class="xref py py-obj docutils literal"><span class="pre">Card</span></tt></a>.</p>
<p>TODO: Write about parameters</p>
<p>If <tt class="xref py py-obj docutils literal"><span class="pre">pos</span></tt> = <tt class="xref py py-obj docutils literal"><span class="pre">None</span></tt>, it can be anywhere. If the card does not exist,
the new card will have the <tt class="xref py py-obj docutils literal"><span class="pre">fix_value</span></tt> as its value when created.
Also check the card’s value by using the <tt class="xref py py-obj docutils literal"><span class="pre">test</span></tt> argument.</p>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.PrimaryHDU.run_option">
<tt class="descname">run_option</tt><big>(</big><em>option='warn'</em>, <em>err_text=''</em>, <em>fix_text='Fixed.'</em>, <em>fix=None</em>, <em>fixable=True</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L26" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.PrimaryHDU.run_option" title="Permalink to this definition">¶</a></dt>
<dd><p>Execute the verification with selected option.</p>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.PrimaryHDU.scale">
<tt class="descname">scale</tt><big>(</big><em>type=None</em>, <em>option='old'</em>, <em>bscale=1</em>, <em>bzero=0</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L311" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.PrimaryHDU.scale" title="Permalink to this definition">¶</a></dt>
<dd><p>Scale image data by using <tt class="docutils literal"><span class="pre">BSCALE</span></tt>/<tt class="docutils literal"><span class="pre">BZERO</span></tt>.</p>
<p>Call to this method will scale <tt class="xref py py-obj docutils literal"><span class="pre">data</span></tt> and update the keywords
of <tt class="docutils literal"><span class="pre">BSCALE</span></tt> and <tt class="docutils literal"><span class="pre">BZERO</span></tt> in <tt class="xref py py-obj docutils literal"><span class="pre">_header</span></tt>. This method should
only be used right before writing to the output file, as the
data will be scaled and is therefore not very usable after the
call.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>type</strong> : str, optional</p>
<blockquote>
<div><p>destination data type, use a string representing a numpy
dtype name, (e.g. <tt class="docutils literal"><span class="pre">'uint8'</span></tt>, <tt class="docutils literal"><span class="pre">'int16'</span></tt>, <tt class="docutils literal"><span class="pre">'float32'</span></tt>
etc.). If is <tt class="xref py py-obj docutils literal"><span class="pre">None</span></tt>, use the current data type.</p>
</div></blockquote>
<p><strong>option</strong> : str</p>
<blockquote>
<div><p>How to scale the data: if <tt class="docutils literal"><span class="pre">"old"</span></tt>, use the original
<tt class="docutils literal"><span class="pre">BSCALE</span></tt> and <tt class="docutils literal"><span class="pre">BZERO</span></tt> values when the data was
read/created. If <tt class="docutils literal"><span class="pre">"minmax"</span></tt>, use the minimum and maximum
of the data to scale. The option will be overwritten by
any user specified <tt class="xref py py-obj docutils literal"><span class="pre">bscale</span></tt>/<tt class="xref py py-obj docutils literal"><span class="pre">bzero</span></tt> values.</p>
</div></blockquote>
<p><strong>bscale, bzero</strong> : int, optional</p>
<blockquote class="last">
<div><p>User-specified <tt class="docutils literal"><span class="pre">BSCALE</span></tt> and <tt class="docutils literal"><span class="pre">BZERO</span></tt> values.</p>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="attribute">
<dt id="astropy.io.fits.PrimaryHDU.section">
<tt class="descname">section</tt><a class="headerlink" href="#astropy.io.fits.PrimaryHDU.section" title="Permalink to this definition">¶</a></dt>
<dd><p>Access a section of the image array without loading the entire array
into memory. The <tt class="xref py py-class docutils literal"><span class="pre">Section</span></tt> object returned by this attribute is
not meant to be used directly by itself. Rather, slices of the section
return the appropriate slice of the data, and loads <em>only</em> that section
into memory.</p>
<p>Sections are mostly obsoleted by memmap support, but should still be
used to deal with very large scaled images. See the
<a class="reference internal" href="../usage/image.html#data-sections"><em>Data Sections</em></a> section of the PyFITS documentation for more
details.</p>
</dd></dl>
<dl class="attribute">
<dt id="astropy.io.fits.PrimaryHDU.shape">
<tt class="descname">shape</tt><a class="headerlink" href="#astropy.io.fits.PrimaryHDU.shape" title="Permalink to this definition">¶</a></dt>
<dd><p>Shape of the image array–should be equivalent to <tt class="docutils literal"><span class="pre">self.data.shape</span></tt>.</p>
</dd></dl>
<dl class="attribute">
<dt id="astropy.io.fits.PrimaryHDU.size">
<tt class="descname">size</tt><a class="headerlink" href="#astropy.io.fits.PrimaryHDU.size" title="Permalink to this definition">¶</a></dt>
<dd><p>Size (in bytes) of the data portion of the HDU.</p>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.PrimaryHDU.update_ext_name">
<tt class="descname">update_ext_name</tt><big>(</big><em>value</em>, <em>comment=None</em>, <em>before=None</em>, <em>after=None</em>, <em>savecomment=False</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L834" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.PrimaryHDU.update_ext_name" title="Permalink to this definition">¶</a></dt>
<dd><p>Update the extension name associated with the HDU.</p>
<p>If the keyword already exists in the Header, it’s value and/or comment
will be updated. If it does not exist, a new card will be created
and it will be placed before or after the specified location.
If no <tt class="xref py py-obj docutils literal"><span class="pre">before</span></tt> or <tt class="xref py py-obj docutils literal"><span class="pre">after</span></tt> is specified, it will be appended at
the end.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>value</strong> : str</p>
<blockquote>
<div><p>value to be used for the new extension name</p>
</div></blockquote>
<p><strong>comment</strong> : str, optional</p>
<blockquote>
<div><p>to be used for updating, default=None.</p>
</div></blockquote>
<p><strong>before</strong> : str or int, optional</p>
<blockquote>
<div><p>name of the keyword, or index of the <a class="reference internal" href="cards.html#astropy.io.fits.Card" title="astropy.io.fits.Card"><tt class="xref py py-obj docutils literal"><span class="pre">Card</span></tt></a> before which
the new card will be placed in the Header. The argument
<tt class="xref py py-obj docutils literal"><span class="pre">before</span></tt> takes precedence over <tt class="xref py py-obj docutils literal"><span class="pre">after</span></tt> if both specified.</p>
</div></blockquote>
<p><strong>after</strong> : str or int, optional</p>
<blockquote>
<div><p>name of the keyword, or index of the <a class="reference internal" href="cards.html#astropy.io.fits.Card" title="astropy.io.fits.Card"><tt class="xref py py-obj docutils literal"><span class="pre">Card</span></tt></a> after which
the new card will be placed in the Header.</p>
</div></blockquote>
<p><strong>savecomment</strong> : bool, optional</p>
<blockquote class="last">
<div><p>When <tt class="xref py py-obj docutils literal"><span class="pre">True</span></tt>, preserve the current comment for an existing
keyword. The argument <tt class="xref py py-obj docutils literal"><span class="pre">savecomment</span></tt> takes precedence over
<tt class="xref py py-obj docutils literal"><span class="pre">comment</span></tt> if both specified. If <tt class="xref py py-obj docutils literal"><span class="pre">comment</span></tt> is not
specified then the current comment will automatically be
preserved.</p>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.PrimaryHDU.update_ext_version">
<tt class="descname">update_ext_version</tt><big>(</big><em>value</em>, <em>comment=None</em>, <em>before=None</em>, <em>after=None</em>, <em>savecomment=False</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L876" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.PrimaryHDU.update_ext_version" title="Permalink to this definition">¶</a></dt>
<dd><p>Update the extension version associated with the HDU.</p>
<p>If the keyword already exists in the Header, it’s value and/or comment
will be updated. If it does not exist, a new card will be created
and it will be placed before or after the specified location.
If no <tt class="xref py py-obj docutils literal"><span class="pre">before</span></tt> or <tt class="xref py py-obj docutils literal"><span class="pre">after</span></tt> is specified, it will be appended at
the end.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>value</strong> : str</p>
<blockquote>
<div><p>value to be used for the new extension version</p>
</div></blockquote>
<p><strong>comment</strong> : str, optional</p>
<blockquote>
<div><p>to be used for updating, default=None.</p>
</div></blockquote>
<p><strong>before</strong> : str or int, optional</p>
<blockquote>
<div><p>name of the keyword, or index of the <a class="reference internal" href="cards.html#astropy.io.fits.Card" title="astropy.io.fits.Card"><tt class="xref py py-obj docutils literal"><span class="pre">Card</span></tt></a> before which
the new card will be placed in the Header. The argument
<tt class="xref py py-obj docutils literal"><span class="pre">before</span></tt> takes precedence over <tt class="xref py py-obj docutils literal"><span class="pre">after</span></tt> if both specified.</p>
</div></blockquote>
<p><strong>after</strong> : str or int, optional</p>
<blockquote>
<div><p>name of the keyword, or index of the <a class="reference internal" href="cards.html#astropy.io.fits.Card" title="astropy.io.fits.Card"><tt class="xref py py-obj docutils literal"><span class="pre">Card</span></tt></a> after which
the new card will be placed in the Header.</p>
</div></blockquote>
<p><strong>savecomment</strong> : bool, optional</p>
<blockquote class="last">
<div><p>When <tt class="xref py py-obj docutils literal"><span class="pre">True</span></tt>, preserve the current comment for an existing
keyword. The argument <tt class="xref py py-obj docutils literal"><span class="pre">savecomment</span></tt> takes precedence over
<tt class="xref py py-obj docutils literal"><span class="pre">comment</span></tt> if both specified. If <tt class="xref py py-obj docutils literal"><span class="pre">comment</span></tt> is not
specified then the current comment will automatically be
preserved.</p>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.PrimaryHDU.verify">
<tt class="descname">verify</tt><big>(</big><em>option='warn'</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L48" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.PrimaryHDU.verify" title="Permalink to this definition">¶</a></dt>
<dd><p>Verify all values in the instance.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>option</strong> : str</p>
<blockquote class="last">
<div><p>Output verification option. Must be one of <tt class="docutils literal"><span class="pre">"fix"</span></tt>,
<tt class="docutils literal"><span class="pre">"silentfix"</span></tt>, <tt class="docutils literal"><span class="pre">"ignore"</span></tt>, <tt class="docutils literal"><span class="pre">"warn"</span></tt>, or
<tt class="docutils literal"><span class="pre">"exception"</span></tt>. See <a class="reference internal" href="verification.html#verify"><em>Verification options</em></a> for more info.</p>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.PrimaryHDU.verify_checksum">
<tt class="descname">verify_checksum</tt><big>(</big><em>blocking='standard'</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L1177" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.PrimaryHDU.verify_checksum" title="Permalink to this definition">¶</a></dt>
<dd><p>Verify that the value in the <tt class="docutils literal"><span class="pre">CHECKSUM</span></tt> keyword matches the
value calculated for the current HDU CHECKSUM.</p>
<dl class="docutils">
<dt>blocking: str, optional</dt>
<dd>“standard” or “nonstandard”, compute sum 2880 bytes at a time, or
not</dd>
</dl>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Returns :</th><td class="field-body"><p class="first"><strong>valid</strong> : int</p>
<blockquote class="last">
<div><ul class="simple">
<li>0 - failure</li>
<li>1 - success</li>
<li>2 - no <tt class="docutils literal"><span class="pre">CHECKSUM</span></tt> keyword present</li>
</ul>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.PrimaryHDU.verify_datasum">
<tt class="descname">verify_datasum</tt><big>(</big><em>blocking='standard'</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L1147" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.PrimaryHDU.verify_datasum" title="Permalink to this definition">¶</a></dt>
<dd><p>Verify that the value in the <tt class="docutils literal"><span class="pre">DATASUM</span></tt> keyword matches the value
calculated for the <tt class="docutils literal"><span class="pre">DATASUM</span></tt> of the current HDU data.</p>
<dl class="docutils">
<dt>blocking: str, optional</dt>
<dd>“standard” or “nonstandard”, compute sum 2880 bytes at a time, or
not</dd>
</dl>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Returns :</th><td class="field-body"><p class="first"><strong>valid</strong> : int</p>
<blockquote class="last">
<div><ul class="simple">
<li>0 - failure</li>
<li>1 - success</li>
<li>2 - no <tt class="docutils literal"><span class="pre">DATASUM</span></tt> keyword present</li>
</ul>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.PrimaryHDU.writeto">
<tt class="descname">writeto</tt><big>(</big><em>name</em>, <em>output_verify='exception'</em>, <em>clobber=False</em>, <em>checksum=False</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L323" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.PrimaryHDU.writeto" title="Permalink to this definition">¶</a></dt>
<dd><p>Write the HDU to a new file. This is a convenience method to
provide a user easier output interface if only one HDU needs
to be written to a file.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>name</strong> : file path, file object or file-like object</p>
<blockquote>
<div><p>Output FITS file. If opened, must be opened for append
(“ab+”)).</p>
</div></blockquote>
<p><strong>output_verify</strong> : str</p>
<blockquote>
<div><p>Output verification option. Must be one of <tt class="docutils literal"><span class="pre">"fix"</span></tt>,
<tt class="docutils literal"><span class="pre">"silentfix"</span></tt>, <tt class="docutils literal"><span class="pre">"ignore"</span></tt>, <tt class="docutils literal"><span class="pre">"warn"</span></tt>, or
<tt class="docutils literal"><span class="pre">"exception"</span></tt>. See <a class="reference internal" href="verification.html#verify"><em>Verification options</em></a> for more info.</p>
</div></blockquote>
<p><strong>clobber</strong> : bool</p>
<blockquote>
<div><p>Overwrite the output file if exists.</p>
</div></blockquote>
<p><strong>checksum</strong> : bool</p>
<blockquote class="last">
<div><p>When <tt class="xref py py-obj docutils literal"><span class="pre">True</span></tt> adds both <tt class="docutils literal"><span class="pre">DATASUM</span></tt> and <tt class="docutils literal"><span class="pre">CHECKSUM</span></tt> cards
to the header of the HDU when written to the file.</p>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
</dd></dl>
</dd></dl>
</div>
<div class="section" id="groupshdu">
<h2><a class="reference internal" href="#astropy.io.fits.GroupsHDU" title="astropy.io.fits.GroupsHDU"><tt class="xref py py-class docutils literal"><span class="pre">GroupsHDU</span></tt></a><a class="headerlink" href="#groupshdu" title="Permalink to this headline">¶</a></h2>
<dl class="class">
<dt id="astropy.io.fits.GroupsHDU">
<em class="property">class </em><tt class="descclassname">astropy.io.fits.</tt><tt class="descname">GroupsHDU</tt><big>(</big><em>data=None</em>, <em>header=None</em>, <em>name=None</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L235" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.GroupsHDU" title="Permalink to this definition">¶</a></dt>
<dd><p>Bases: <tt class="xref py py-class docutils literal"><span class="pre">astropy.io.fits.hdu.image.PrimaryHDU</span></tt>, <tt class="xref py py-class docutils literal"><span class="pre">astropy.io.fits.hdu.table._TableLikeHDU</span></tt></p>
<p>FITS Random Groups HDU class.</p>
<dl class="method">
<dt id="astropy.io.fits.GroupsHDU.add_checksum">
<tt class="descname">add_checksum</tt><big>(</big><em>when=None</em>, <em>override_datasum=False</em>, <em>blocking='standard'</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L1099" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.GroupsHDU.add_checksum" title="Permalink to this definition">¶</a></dt>
<dd><p>Add the <tt class="docutils literal"><span class="pre">CHECKSUM</span></tt> and <tt class="docutils literal"><span class="pre">DATASUM</span></tt> cards to this HDU with
the values set to the checksum calculated for the HDU and the
data respectively. The addition of the <tt class="docutils literal"><span class="pre">DATASUM</span></tt> card may
be overridden.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>when</strong> : str, optional</p>
<blockquote>
<div><p>comment string for the cards; by default the comments
will represent the time when the checksum was calculated</p>
</div></blockquote>
<p><strong>override_datasum</strong> : bool, optional</p>
<blockquote>
<div><p>add the <tt class="docutils literal"><span class="pre">CHECKSUM</span></tt> card only</p>
</div></blockquote>
<p><strong>blocking: str, optional</strong> :</p>
<blockquote class="last">
<div><p>“standard” or “nonstandard”, compute sum 2880 bytes at a time, or
not</p>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
<p class="rubric">Notes</p>
<p>For testing purposes, first call <a class="reference internal" href="#astropy.io.fits.GroupsHDU.add_datasum" title="astropy.io.fits.GroupsHDU.add_datasum"><tt class="xref py py-obj docutils literal"><span class="pre">add_datasum</span></tt></a> with a <tt class="xref py py-obj docutils literal"><span class="pre">when</span></tt>
argument, then call <a class="reference internal" href="#astropy.io.fits.GroupsHDU.add_checksum" title="astropy.io.fits.GroupsHDU.add_checksum"><tt class="xref py py-obj docutils literal"><span class="pre">add_checksum</span></tt></a> with a <tt class="xref py py-obj docutils literal"><span class="pre">when</span></tt> argument and
<tt class="xref py py-obj docutils literal"><span class="pre">override_datasum</span></tt> set to <tt class="xref py py-obj docutils literal"><span class="pre">True</span></tt>. This will provide
consistent comments for both cards and enable the generation
of a <tt class="docutils literal"><span class="pre">CHECKSUM</span></tt> card with a consistent value.</p>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.GroupsHDU.add_datasum">
<tt class="descname">add_datasum</tt><big>(</big><em>when=None</em>, <em>blocking='standard'</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L1063" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.GroupsHDU.add_datasum" title="Permalink to this definition">¶</a></dt>
<dd><p>Add the <tt class="docutils literal"><span class="pre">DATASUM</span></tt> card to this HDU with the value set to the
checksum calculated for the data.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>when</strong> : str, optional</p>
<blockquote>
<div><p>Comment string for the card that by default represents the
time when the checksum was calculated</p>
</div></blockquote>
<p><strong>blocking: str, optional</strong> :</p>
<blockquote>
<div><p>“standard” or “nonstandard”, compute sum 2880 bytes at a time, or
not</p>
</div></blockquote>
</td>
</tr>
<tr class="field-even field"><th class="field-name">Returns :</th><td class="field-body"><p class="first"><strong>checksum</strong> : int</p>
<blockquote class="last">
<div><p>The calculated datasum</p>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
<p class="rubric">Notes</p>
<p>For testing purposes, provide a <tt class="xref py py-obj docutils literal"><span class="pre">when</span></tt> argument to enable the
comment value in the card to remain consistent. This will
enable the generation of a <tt class="docutils literal"><span class="pre">CHECKSUM</span></tt> card with a consistent
value.</p>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.GroupsHDU.copy">
<tt class="descname">copy</tt><big>(</big><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L819" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.GroupsHDU.copy" title="Permalink to this definition">¶</a></dt>
<dd><p>Make a copy of the HDU, both header and data are copied.</p>
</dd></dl>
<dl class="attribute">
<dt id="astropy.io.fits.GroupsHDU.data">
<tt class="descname">data</tt><a class="headerlink" href="#astropy.io.fits.GroupsHDU.data" title="Permalink to this definition">¶</a></dt>
<dd><p>The data of a random group FITS file will be like a binary table’s
data.</p>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.GroupsHDU.filebytes">
<tt class="descname">filebytes</tt><big>(</big><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L761" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.GroupsHDU.filebytes" title="Permalink to this definition">¶</a></dt>
<dd><p>Calculates and returns the number of bytes that this HDU will write to
a file.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><strong>None</strong> :</td>
</tr>
<tr class="field-even field"><th class="field-name">Returns :</th><td class="field-body"><strong>Number of bytes</strong> :</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.GroupsHDU.fileinfo">
<tt class="descname">fileinfo</tt><big>(</big><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L779" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.GroupsHDU.fileinfo" title="Permalink to this definition">¶</a></dt>
<dd><p>Returns a dictionary detailing information about the locations
of this HDU within any associated file. The values are only
valid after a read or write of the associated file with no
intervening changes to the <a class="reference internal" href="hdulists.html#astropy.io.fits.HDUList" title="astropy.io.fits.HDUList"><tt class="xref py py-obj docutils literal"><span class="pre">HDUList</span></tt></a>.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>None</strong> :</p>
</td>
</tr>
<tr class="field-even field"><th class="field-name">Returns :</th><td class="field-body"><p class="first"><strong>dictionary or None</strong> :</p>
<blockquote class="last">
<div><p>The dictionary details information about the locations of
this HDU within an associated file. Returns <tt class="xref py py-obj docutils literal"><span class="pre">None</span></tt> when
the HDU is not associated with a file.</p>
<p>Dictionary contents:</p>
<table border="1" class="docutils">
<colgroup>
<col width="15%" />
<col width="85%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Key</th>
<th class="head">Value</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td>file</td>
<td>File object associated with the HDU</td>
</tr>
<tr class="row-odd"><td>filemode</td>
<td>Mode in which the file was opened (readonly, copyonwrite,
update, append, ostream)</td>
</tr>
<tr class="row-even"><td>hdrLoc</td>
<td>Starting byte location of header in file</td>
</tr>
<tr class="row-odd"><td>datLoc</td>
<td>Starting byte location of data block in file</td>
</tr>
<tr class="row-even"><td>datSpan</td>
<td>Data size including padding</td>
</tr>
</tbody>
</table>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="classmethod">
<dt id="astropy.io.fits.GroupsHDU.fromstring">
<em class="property">classmethod </em><tt class="descname">fromstring</tt><big>(</big><em>data</em>, <em>fileobj=None</em>, <em>offset=0</em>, <em>checksum=False</em>, <em>ignore_missing_end=False</em>, <em>**kwargs</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L166" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.GroupsHDU.fromstring" title="Permalink to this definition">¶</a></dt>
<dd><p>Creates a new HDU object of the appropriate type from a string
containing the HDU’s entire header and, optionally, its data.</p>
<p>Note: When creating a new HDU from a string without a backing file
object, the data of that HDU may be read-only. It depends on whether
the underlying string was an immutable Python str/bytes object, or some
kind of read-write memory buffer such as a <tt class="xref py py-obj docutils literal"><span class="pre">memoryview</span></tt>.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>data</strong> : str, bytearray, memoryview, ndarray</p>
<blockquote>
<div><p>A byte string contining the HDU’s header and, optionally, its data.
If <tt class="xref py py-obj docutils literal"><span class="pre">fileobj</span></tt> is not specified, and the length of <a class="reference internal" href="#astropy.io.fits.GroupsHDU.data" title="astropy.io.fits.GroupsHDU.data"><tt class="xref py py-obj docutils literal"><span class="pre">data</span></tt></a> extends
beyond the header, then the trailing data is taken to be the HDU’s
data. If <tt class="xref py py-obj docutils literal"><span class="pre">fileobj</span></tt> is specified then the trailing data is ignored.</p>
</div></blockquote>
<p><strong>fileobj</strong> : file (optional)</p>
<blockquote>
<div><p>The file-like object that this HDU was read from.</p>
</div></blockquote>
<p><strong>offset</strong> : int (optional)</p>
<blockquote>
<div><p>If <tt class="xref py py-obj docutils literal"><span class="pre">fileobj</span></tt> is specified, the offset into the file-like object at
which this HDU begins.</p>
</div></blockquote>
<p><strong>checksum</strong> : bool (optional)</p>
<blockquote>
<div><p>Check the HDU’s checksum and/or datasum.</p>
</div></blockquote>
<p><strong>ignore_missing_end</strong> : bool (optional)</p>
<blockquote>
<div><p>Ignore a missing end card in the header data. Note that without
the end card the end of the header can’t be found, so the entire
data is just assumed to be the header.</p>
</div></blockquote>
<p><strong>kwargs</strong> : (optional)</p>
<blockquote class="last">
<div><p>May contain additional keyword arguments specific to an HDU type.
Any unrecognized kwargs are simply ignored.</p>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="attribute">
<dt id="astropy.io.fits.GroupsHDU.parnames">
<tt class="descname">parnames</tt><a class="headerlink" href="#astropy.io.fits.GroupsHDU.parnames" title="Permalink to this definition">¶</a></dt>
<dd><p>The names of the group parameters as described by the header.</p>
</dd></dl>
<dl class="classmethod">
<dt id="astropy.io.fits.GroupsHDU.readfrom">
<em class="property">classmethod </em><tt class="descname">readfrom</tt><big>(</big><em>fileobj</em>, <em>checksum=False</em>, <em>ignore_missing_end=False</em>, <em>**kwargs</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L282" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.GroupsHDU.readfrom" title="Permalink to this definition">¶</a></dt>
<dd><p>Read the HDU from a file. Normally an HDU should be opened with
<tt class="xref py py-obj docutils literal"><span class="pre">fitsopen()</span></tt> which reads the entire HDU list in a FITS file. But this
method is still provided for symmetry with <a class="reference internal" href="files.html#astropy.io.fits.writeto" title="astropy.io.fits.writeto"><tt class="xref py py-obj docutils literal"><span class="pre">writeto()</span></tt></a>.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>fileobj</strong> : file object or file-like object</p>
<blockquote>
<div><p>Input FITS file. The file’s seek pointer is assumed to be at the
beginning of the HDU.</p>
</div></blockquote>
<p><strong>checksum</strong> : bool</p>
<blockquote>
<div><p>If <tt class="xref py py-obj docutils literal"><span class="pre">True</span></tt>, verifies that both <tt class="docutils literal"><span class="pre">DATASUM</span></tt> and
<tt class="docutils literal"><span class="pre">CHECKSUM</span></tt> card values (when present in the HDU header)
match the header and data of all HDU’s in the file.</p>
</div></blockquote>
<p><strong>ignore_missing_end</strong> : bool</p>
<blockquote class="last">
<div><p>Do not issue an exception when opening a file that is
missing an <tt class="docutils literal"><span class="pre">END</span></tt> card in the last header.</p>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.GroupsHDU.req_cards">
<tt class="descname">req_cards</tt><big>(</big><em>keyword</em>, <em>pos</em>, <em>test</em>, <em>fix_value</em>, <em>option</em>, <em>errlist</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L985" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.GroupsHDU.req_cards" title="Permalink to this definition">¶</a></dt>
<dd><p>Check the existence, location, and value of a required <a class="reference internal" href="cards.html#astropy.io.fits.Card" title="astropy.io.fits.Card"><tt class="xref py py-obj docutils literal"><span class="pre">Card</span></tt></a>.</p>
<p>TODO: Write about parameters</p>
<p>If <tt class="xref py py-obj docutils literal"><span class="pre">pos</span></tt> = <tt class="xref py py-obj docutils literal"><span class="pre">None</span></tt>, it can be anywhere. If the card does not exist,
the new card will have the <tt class="xref py py-obj docutils literal"><span class="pre">fix_value</span></tt> as its value when created.
Also check the card’s value by using the <tt class="xref py py-obj docutils literal"><span class="pre">test</span></tt> argument.</p>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.GroupsHDU.run_option">
<tt class="descname">run_option</tt><big>(</big><em>option='warn'</em>, <em>err_text=''</em>, <em>fix_text='Fixed.'</em>, <em>fix=None</em>, <em>fixable=True</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L26" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.GroupsHDU.run_option" title="Permalink to this definition">¶</a></dt>
<dd><p>Execute the verification with selected option.</p>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.GroupsHDU.scale">
<tt class="descname">scale</tt><big>(</big><em>type=None</em>, <em>option='old'</em>, <em>bscale=1</em>, <em>bzero=0</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L311" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.GroupsHDU.scale" title="Permalink to this definition">¶</a></dt>
<dd><p>Scale image data by using <tt class="docutils literal"><span class="pre">BSCALE</span></tt>/<tt class="docutils literal"><span class="pre">BZERO</span></tt>.</p>
<p>Call to this method will scale <a class="reference internal" href="#astropy.io.fits.GroupsHDU.data" title="astropy.io.fits.GroupsHDU.data"><tt class="xref py py-obj docutils literal"><span class="pre">data</span></tt></a> and update the keywords
of <tt class="docutils literal"><span class="pre">BSCALE</span></tt> and <tt class="docutils literal"><span class="pre">BZERO</span></tt> in <tt class="xref py py-obj docutils literal"><span class="pre">_header</span></tt>. This method should
only be used right before writing to the output file, as the
data will be scaled and is therefore not very usable after the
call.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>type</strong> : str, optional</p>
<blockquote>
<div><p>destination data type, use a string representing a numpy
dtype name, (e.g. <tt class="docutils literal"><span class="pre">'uint8'</span></tt>, <tt class="docutils literal"><span class="pre">'int16'</span></tt>, <tt class="docutils literal"><span class="pre">'float32'</span></tt>
etc.). If is <tt class="xref py py-obj docutils literal"><span class="pre">None</span></tt>, use the current data type.</p>
</div></blockquote>
<p><strong>option</strong> : str</p>
<blockquote>
<div><p>How to scale the data: if <tt class="docutils literal"><span class="pre">"old"</span></tt>, use the original
<tt class="docutils literal"><span class="pre">BSCALE</span></tt> and <tt class="docutils literal"><span class="pre">BZERO</span></tt> values when the data was
read/created. If <tt class="docutils literal"><span class="pre">"minmax"</span></tt>, use the minimum and maximum
of the data to scale. The option will be overwritten by
any user specified <tt class="xref py py-obj docutils literal"><span class="pre">bscale</span></tt>/<tt class="xref py py-obj docutils literal"><span class="pre">bzero</span></tt> values.</p>
</div></blockquote>
<p><strong>bscale, bzero</strong> : int, optional</p>
<blockquote class="last">
<div><p>User-specified <tt class="docutils literal"><span class="pre">BSCALE</span></tt> and <tt class="docutils literal"><span class="pre">BZERO</span></tt> values.</p>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="attribute">
<dt id="astropy.io.fits.GroupsHDU.section">
<tt class="descname">section</tt><a class="headerlink" href="#astropy.io.fits.GroupsHDU.section" title="Permalink to this definition">¶</a></dt>
<dd><p>Access a section of the image array without loading the entire array
into memory. The <tt class="xref py py-class docutils literal"><span class="pre">Section</span></tt> object returned by this attribute is
not meant to be used directly by itself. Rather, slices of the section
return the appropriate slice of the data, and loads <em>only</em> that section
into memory.</p>
<p>Sections are mostly obsoleted by memmap support, but should still be
used to deal with very large scaled images. See the
<a class="reference internal" href="../usage/image.html#data-sections"><em>Data Sections</em></a> section of the PyFITS documentation for more
details.</p>
</dd></dl>
<dl class="attribute">
<dt id="astropy.io.fits.GroupsHDU.shape">
<tt class="descname">shape</tt><a class="headerlink" href="#astropy.io.fits.GroupsHDU.shape" title="Permalink to this definition">¶</a></dt>
<dd><p>Shape of the image array–should be equivalent to <tt class="docutils literal"><span class="pre">self.data.shape</span></tt>.</p>
</dd></dl>
<dl class="attribute">
<dt id="astropy.io.fits.GroupsHDU.size">
<tt class="descname">size</tt><a class="headerlink" href="#astropy.io.fits.GroupsHDU.size" title="Permalink to this definition">¶</a></dt>
<dd><p>Returns the size (in bytes) of the HDU’s data part.</p>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.GroupsHDU.update_ext_name">
<tt class="descname">update_ext_name</tt><big>(</big><em>value</em>, <em>comment=None</em>, <em>before=None</em>, <em>after=None</em>, <em>savecomment=False</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L834" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.GroupsHDU.update_ext_name" title="Permalink to this definition">¶</a></dt>
<dd><p>Update the extension name associated with the HDU.</p>
<p>If the keyword already exists in the Header, it’s value and/or comment
will be updated. If it does not exist, a new card will be created
and it will be placed before or after the specified location.
If no <tt class="xref py py-obj docutils literal"><span class="pre">before</span></tt> or <tt class="xref py py-obj docutils literal"><span class="pre">after</span></tt> is specified, it will be appended at
the end.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>value</strong> : str</p>
<blockquote>
<div><p>value to be used for the new extension name</p>
</div></blockquote>
<p><strong>comment</strong> : str, optional</p>
<blockquote>
<div><p>to be used for updating, default=None.</p>
</div></blockquote>
<p><strong>before</strong> : str or int, optional</p>
<blockquote>
<div><p>name of the keyword, or index of the <a class="reference internal" href="cards.html#astropy.io.fits.Card" title="astropy.io.fits.Card"><tt class="xref py py-obj docutils literal"><span class="pre">Card</span></tt></a> before which
the new card will be placed in the Header. The argument
<tt class="xref py py-obj docutils literal"><span class="pre">before</span></tt> takes precedence over <tt class="xref py py-obj docutils literal"><span class="pre">after</span></tt> if both specified.</p>
</div></blockquote>
<p><strong>after</strong> : str or int, optional</p>
<blockquote>
<div><p>name of the keyword, or index of the <a class="reference internal" href="cards.html#astropy.io.fits.Card" title="astropy.io.fits.Card"><tt class="xref py py-obj docutils literal"><span class="pre">Card</span></tt></a> after which
the new card will be placed in the Header.</p>
</div></blockquote>
<p><strong>savecomment</strong> : bool, optional</p>
<blockquote class="last">
<div><p>When <tt class="xref py py-obj docutils literal"><span class="pre">True</span></tt>, preserve the current comment for an existing
keyword. The argument <tt class="xref py py-obj docutils literal"><span class="pre">savecomment</span></tt> takes precedence over
<tt class="xref py py-obj docutils literal"><span class="pre">comment</span></tt> if both specified. If <tt class="xref py py-obj docutils literal"><span class="pre">comment</span></tt> is not
specified then the current comment will automatically be
preserved.</p>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.GroupsHDU.update_ext_version">
<tt class="descname">update_ext_version</tt><big>(</big><em>value</em>, <em>comment=None</em>, <em>before=None</em>, <em>after=None</em>, <em>savecomment=False</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L876" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.GroupsHDU.update_ext_version" title="Permalink to this definition">¶</a></dt>
<dd><p>Update the extension version associated with the HDU.</p>
<p>If the keyword already exists in the Header, it’s value and/or comment
will be updated. If it does not exist, a new card will be created
and it will be placed before or after the specified location.
If no <tt class="xref py py-obj docutils literal"><span class="pre">before</span></tt> or <tt class="xref py py-obj docutils literal"><span class="pre">after</span></tt> is specified, it will be appended at
the end.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>value</strong> : str</p>
<blockquote>
<div><p>value to be used for the new extension version</p>
</div></blockquote>
<p><strong>comment</strong> : str, optional</p>
<blockquote>
<div><p>to be used for updating, default=None.</p>
</div></blockquote>
<p><strong>before</strong> : str or int, optional</p>
<blockquote>
<div><p>name of the keyword, or index of the <a class="reference internal" href="cards.html#astropy.io.fits.Card" title="astropy.io.fits.Card"><tt class="xref py py-obj docutils literal"><span class="pre">Card</span></tt></a> before which
the new card will be placed in the Header. The argument
<tt class="xref py py-obj docutils literal"><span class="pre">before</span></tt> takes precedence over <tt class="xref py py-obj docutils literal"><span class="pre">after</span></tt> if both specified.</p>
</div></blockquote>
<p><strong>after</strong> : str or int, optional</p>
<blockquote>
<div><p>name of the keyword, or index of the <a class="reference internal" href="cards.html#astropy.io.fits.Card" title="astropy.io.fits.Card"><tt class="xref py py-obj docutils literal"><span class="pre">Card</span></tt></a> after which
the new card will be placed in the Header.</p>
</div></blockquote>
<p><strong>savecomment</strong> : bool, optional</p>
<blockquote class="last">
<div><p>When <tt class="xref py py-obj docutils literal"><span class="pre">True</span></tt>, preserve the current comment for an existing
keyword. The argument <tt class="xref py py-obj docutils literal"><span class="pre">savecomment</span></tt> takes precedence over
<tt class="xref py py-obj docutils literal"><span class="pre">comment</span></tt> if both specified. If <tt class="xref py py-obj docutils literal"><span class="pre">comment</span></tt> is not
specified then the current comment will automatically be
preserved.</p>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.GroupsHDU.verify">
<tt class="descname">verify</tt><big>(</big><em>option='warn'</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L48" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.GroupsHDU.verify" title="Permalink to this definition">¶</a></dt>
<dd><p>Verify all values in the instance.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>option</strong> : str</p>
<blockquote class="last">
<div><p>Output verification option. Must be one of <tt class="docutils literal"><span class="pre">"fix"</span></tt>,
<tt class="docutils literal"><span class="pre">"silentfix"</span></tt>, <tt class="docutils literal"><span class="pre">"ignore"</span></tt>, <tt class="docutils literal"><span class="pre">"warn"</span></tt>, or
<tt class="docutils literal"><span class="pre">"exception"</span></tt>. See <a class="reference internal" href="verification.html#verify"><em>Verification options</em></a> for more info.</p>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.GroupsHDU.verify_checksum">
<tt class="descname">verify_checksum</tt><big>(</big><em>blocking='standard'</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L1177" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.GroupsHDU.verify_checksum" title="Permalink to this definition">¶</a></dt>
<dd><p>Verify that the value in the <tt class="docutils literal"><span class="pre">CHECKSUM</span></tt> keyword matches the
value calculated for the current HDU CHECKSUM.</p>
<dl class="docutils">
<dt>blocking: str, optional</dt>
<dd>“standard” or “nonstandard”, compute sum 2880 bytes at a time, or
not</dd>
</dl>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Returns :</th><td class="field-body"><p class="first"><strong>valid</strong> : int</p>
<blockquote class="last">
<div><ul class="simple">
<li>0 - failure</li>
<li>1 - success</li>
<li>2 - no <tt class="docutils literal"><span class="pre">CHECKSUM</span></tt> keyword present</li>
</ul>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.GroupsHDU.verify_datasum">
<tt class="descname">verify_datasum</tt><big>(</big><em>blocking='standard'</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L1147" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.GroupsHDU.verify_datasum" title="Permalink to this definition">¶</a></dt>
<dd><p>Verify that the value in the <tt class="docutils literal"><span class="pre">DATASUM</span></tt> keyword matches the value
calculated for the <tt class="docutils literal"><span class="pre">DATASUM</span></tt> of the current HDU data.</p>
<dl class="docutils">
<dt>blocking: str, optional</dt>
<dd>“standard” or “nonstandard”, compute sum 2880 bytes at a time, or
not</dd>
</dl>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Returns :</th><td class="field-body"><p class="first"><strong>valid</strong> : int</p>
<blockquote class="last">
<div><ul class="simple">
<li>0 - failure</li>
<li>1 - success</li>
<li>2 - no <tt class="docutils literal"><span class="pre">DATASUM</span></tt> keyword present</li>
</ul>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.GroupsHDU.writeto">
<tt class="descname">writeto</tt><big>(</big><em>name</em>, <em>output_verify='exception'</em>, <em>clobber=False</em>, <em>checksum=False</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L323" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.GroupsHDU.writeto" title="Permalink to this definition">¶</a></dt>
<dd><p>Write the HDU to a new file. This is a convenience method to
provide a user easier output interface if only one HDU needs
to be written to a file.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>name</strong> : file path, file object or file-like object</p>
<blockquote>
<div><p>Output FITS file. If opened, must be opened for append
(“ab+”)).</p>
</div></blockquote>
<p><strong>output_verify</strong> : str</p>
<blockquote>
<div><p>Output verification option. Must be one of <tt class="docutils literal"><span class="pre">"fix"</span></tt>,
<tt class="docutils literal"><span class="pre">"silentfix"</span></tt>, <tt class="docutils literal"><span class="pre">"ignore"</span></tt>, <tt class="docutils literal"><span class="pre">"warn"</span></tt>, or
<tt class="docutils literal"><span class="pre">"exception"</span></tt>. See <a class="reference internal" href="verification.html#verify"><em>Verification options</em></a> for more info.</p>
</div></blockquote>
<p><strong>clobber</strong> : bool</p>
<blockquote>
<div><p>Overwrite the output file if exists.</p>
</div></blockquote>
<p><strong>checksum</strong> : bool</p>
<blockquote class="last">
<div><p>When <tt class="xref py py-obj docutils literal"><span class="pre">True</span></tt> adds both <tt class="docutils literal"><span class="pre">DATASUM</span></tt> and <tt class="docutils literal"><span class="pre">CHECKSUM</span></tt> cards
to the header of the HDU when written to the file.</p>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
</dd></dl>
</dd></dl>
</div>
<div class="section" id="groupdata">
<h2><a class="reference internal" href="#astropy.io.fits.GroupData" title="astropy.io.fits.GroupData"><tt class="xref py py-class docutils literal"><span class="pre">GroupData</span></tt></a><a class="headerlink" href="#groupdata" title="Permalink to this headline">¶</a></h2>
<dl class="class">
<dt id="astropy.io.fits.GroupData">
<em class="property">class </em><tt class="descclassname">astropy.io.fits.</tt><tt class="descname">GroupData</tt><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L86" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.GroupData" title="Permalink to this definition">¶</a></dt>
<dd><p>Bases: <tt class="xref py py-class docutils literal"><span class="pre">astropy.io.fits.fitsrec.FITS_rec</span></tt></p>
<p>Random groups data object.</p>
<p>Allows structured access to FITS Group data in a manner analogous
to tables.</p>
<dl class="method">
<dt id="astropy.io.fits.GroupData.par">
<tt class="descname">par</tt><big>(</big><em>parname</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L214" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.GroupData.par" title="Permalink to this definition">¶</a></dt>
<dd><p>Get the group parameter values.</p>
</dd></dl>
</dd></dl>
</div>
<div class="section" id="group">
<h2><tt class="xref py py-class docutils literal"><span class="pre">Group</span></tt><a class="headerlink" href="#group" title="Permalink to this headline">¶</a></h2>
<dl class="class">
<dt>
<em class="property">class </em><tt class="descclassname">astropy.io.fits.</tt><tt class="descname">GroupData</tt><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L86" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a></dt>
<dd><p>Bases: <tt class="xref py py-class docutils literal"><span class="pre">astropy.io.fits.fitsrec.FITS_rec</span></tt></p>
<p>Random groups data object.</p>
<p>Allows structured access to FITS Group data in a manner analogous
to tables.</p>
<dl class="method">
<dt>
<tt class="descname">par</tt><big>(</big><em>parname</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L214" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a></dt>
<dd><p>Get the group parameter values.</p>
</dd></dl>
</dd></dl>
</div>
<div class="section" id="streaminghdu">
<h2><a class="reference internal" href="#astropy.io.fits.StreamingHDU" title="astropy.io.fits.StreamingHDU"><tt class="xref py py-class docutils literal"><span class="pre">StreamingHDU</span></tt></a><a class="headerlink" href="#streaminghdu" title="Permalink to this headline">¶</a></h2>
<dl class="class">
<dt id="astropy.io.fits.StreamingHDU">
<em class="property">class </em><tt class="descclassname">astropy.io.fits.</tt><tt class="descname">StreamingHDU</tt><big>(</big><em>name</em>, <em>header</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L15" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.StreamingHDU" title="Permalink to this definition">¶</a></dt>
<dd><p>Bases: <tt class="xref py py-class docutils literal"><span class="pre">object</span></tt></p>
<p>A class that provides the capability to stream data to a FITS file
instead of requiring data to all be written at once.</p>
<p>The following pseudocode illustrates its use:</p>
<div class="highlight-python"><pre>header = astropy.io.fits.Header()
for all the cards you need in the header:
header[key] = (value, comment)
shdu = astropy.io.fits.StreamingHDU('filename.fits', header)
for each piece of data:
shdu.write(data)
shdu.close()</pre>
</div>
<dl class="method">
<dt id="astropy.io.fits.StreamingHDU.close">
<tt class="descname">close</tt><big>(</big><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L229" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.StreamingHDU.close" title="Permalink to this definition">¶</a></dt>
<dd><p>Close the physical FITS file.</p>
</dd></dl>
<dl class="attribute">
<dt id="astropy.io.fits.StreamingHDU.size">
<tt class="descname">size</tt><a class="headerlink" href="#astropy.io.fits.StreamingHDU.size" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the size (in bytes) of the data portion of the HDU.</p>
</dd></dl>
<dl class="method">
<dt id="astropy.io.fits.StreamingHDU.write">
<tt class="descname">write</tt><big>(</big><em>data</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/io/fits.py#L140" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="headerlink" href="#astropy.io.fits.StreamingHDU.write" title="Permalink to this definition">¶</a></dt>
<dd><p>Write the given data to the stream.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>data</strong> : ndarray</p>
<blockquote>
<div><p>Data to stream to the file.</p>
</div></blockquote>
</td>
</tr>
<tr class="field-even field"><th class="field-name">Returns :</th><td class="field-body"><p class="first"><strong>writecomplete</strong> : int</p>
<blockquote class="last">
<div><p>Flag that when <tt class="xref py py-obj docutils literal"><span class="pre">True</span></tt> indicates that all of the required
data has been written to the stream.</p>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
<p class="rubric">Notes</p>
<p>Only the amount of data specified in the header provided to
the class constructor may be written to the stream. If the
provided data would cause the stream to overflow, an <tt class="xref py py-obj docutils literal"><span class="pre">IOError</span></tt>
exception is raised and the data is not written. Once
sufficient data has been written to the stream to satisfy the
amount specified in the header, the stream is padded to fill a
complete FITS block and no more data will be accepted. An
attempt to write more data after the stream has been filled
will raise an <tt class="xref py py-obj docutils literal"><span class="pre">IOError</span></tt> exception. If the dtype of the input
data does not match what is expected by the header, a
<tt class="xref py py-obj docutils literal"><span class="pre">TypeError</span></tt> exception is raised.</p>
</dd></dl>
</dd></dl>
</div>
</div>
</div>
</div>
</div>
<div class="sphinxsidebar">
<div class="sphinxsidebarwrapper"><h3>Page Contents</h3>
<ul>
<li><a class="reference internal" href="#">Header Data Units</a><ul>
<li><a class="reference internal" href="#primaryhdu"><tt class="docutils literal"><span class="pre">PrimaryHDU</span></tt></a></li>
<li><a class="reference internal" href="#groupshdu"><tt class="docutils literal"><span class="pre">GroupsHDU</span></tt></a></li>
<li><a class="reference internal" href="#groupdata"><tt class="docutils literal"><span class="pre">GroupData</span></tt></a></li>
<li><a class="reference internal" href="#group"><tt class="docutils literal"><span class="pre">Group</span></tt></a></li>
<li><a class="reference internal" href="#streaminghdu"><tt class="docutils literal"><span class="pre">StreamingHDU</span></tt></a></li>
</ul>
</li>
</ul>
</div>
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