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<li><a href="../units/index.html" accesskey="U">Units (<tt class="docutils literal"><span class="pre">astropy.units</span></tt>)</a> »</li>
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<div class="section" id="unit">
<h1>Unit<a class="headerlink" href="#unit" title="Permalink to this headline">¶</a></h1>
<dl class="class">
<dt id="astropy.units.core.Unit">
<em class="property">class </em><tt class="descclassname">astropy.units.core.</tt><tt class="descname">Unit</tt><big>(</big><em>st</em>, <em>represents=None</em>, <em>register=False</em>, <em>doc=None</em>, <em>format=None</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/units/core.py#L1056" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="reference internal" href="../_modules/astropy/units/core.html#Unit"><span class="viewcode-link">[source]</span></a><a class="headerlink" href="#astropy.units.core.Unit" title="Permalink to this definition">¶</a></dt>
<dd><p>Bases: <a class="reference internal" href="astropy.units.core.NamedUnit.html#astropy.units.core.NamedUnit" title="astropy.units.core.NamedUnit"><tt class="xref py py-class docutils literal"><span class="pre">astropy.units.core.NamedUnit</span></tt></a></p>
<p>The main unit class.</p>
<p>There are a number of different ways to construct a Unit, but
always returns a <a class="reference internal" href="astropy.units.core.UnitBase.html#astropy.units.core.UnitBase" title="astropy.units.core.UnitBase"><tt class="xref py py-obj docutils literal"><span class="pre">UnitBase</span></tt></a> instance. If the arguments refer to
an already-existing unit, that existing unit instance is returned,
rather than a new one.</p>
<ul>
<li><p class="first">From a string:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">Unit</span><span class="p">(</span><span class="n">s</span><span class="p">,</span> <span class="n">format</span><span class="o">=</span><span class="bp">None</span><span class="p">,</span> <span class="n">parse_strict</span><span class="o">=</span><span class="s">'silent'</span><span class="p">)</span>
</pre></div>
</div>
<p>Construct from a string representing a (possibly compound) unit.</p>
<p>The optional <tt class="xref py py-obj docutils literal"><span class="pre">format</span></tt> keyword argument specifies the format the
string is in, by default <tt class="docutils literal"><span class="pre">"generic"</span></tt>. For a description of
the available formats, see <a class="reference internal" href="../units/index.html#module-astropy.units.format" title="astropy.units.format"><tt class="xref py py-obj docutils literal"><span class="pre">astropy.units.format</span></tt></a>.</p>
<p>The optional <tt class="xref py py-obj docutils literal"><span class="pre">parse_strict</span></tt> keyword controls what happens when an
unrecognized unit string is passed in. It may be one of the following:</p>
<blockquote>
<div><ul class="simple">
<li><tt class="docutils literal"><span class="pre">'raise'</span></tt>: (default) raise a ValueError exception.</li>
<li><tt class="docutils literal"><span class="pre">'warn'</span></tt>: emit a Warning, and return an
<a class="reference internal" href="astropy.units.core.UnrecognizedUnit.html#astropy.units.core.UnrecognizedUnit" title="astropy.units.core.UnrecognizedUnit"><tt class="xref py py-obj docutils literal"><span class="pre">UnrecognizedUnit</span></tt></a> instance.</li>
<li><tt class="docutils literal"><span class="pre">'silent'</span></tt>: return an <a class="reference internal" href="astropy.units.core.UnrecognizedUnit.html#astropy.units.core.UnrecognizedUnit" title="astropy.units.core.UnrecognizedUnit"><tt class="xref py py-obj docutils literal"><span class="pre">UnrecognizedUnit</span></tt></a> instance.</li>
</ul>
</div></blockquote>
</li>
<li><p class="first">From a number:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">Unit</span><span class="p">(</span><span class="n">number</span><span class="p">)</span>
</pre></div>
</div>
<p>Creates a dimensionless unit.</p>
</li>
<li><p class="first">From a <a class="reference internal" href="astropy.units.core.UnitBase.html#astropy.units.core.UnitBase" title="astropy.units.core.UnitBase"><tt class="xref py py-obj docutils literal"><span class="pre">UnitBase</span></tt></a> instance:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">Unit</span><span class="p">(</span><span class="n">unit</span><span class="p">)</span>
</pre></div>
</div>
<p>Returns the given unit unchanged.</p>
</li>
<li><p class="first">From <tt class="xref py py-obj docutils literal"><span class="pre">None</span></tt>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">Unit</span><span class="p">()</span>
</pre></div>
</div>
<p>Returns the null unit.</p>
</li>
<li><p class="first">The last form, which creates a new <a class="reference internal" href="#astropy.units.core.Unit" title="astropy.units.core.Unit"><tt class="xref py py-obj docutils literal"><span class="pre">Unit</span></tt></a> is described in detail
below.</p>
</li>
</ul>
<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>st</strong> : str or list of str</p>
<blockquote>
<div><p>The name of the unit. If a list, the first element is the
canonical (short) name, and the rest of the elements are
aliases.</p>
</div></blockquote>
<p><strong>represents</strong> : UnitBase instance</p>
<blockquote>
<div><p>The unit that this named unit represents.</p>
</div></blockquote>
<p><strong>register</strong> : boolean, optional</p>
<blockquote>
<div><p>When <tt class="xref py py-obj docutils literal"><span class="pre">True</span></tt>, also register the unit in the standard unit
namespace. Default is <tt class="xref py py-obj docutils literal"><span class="pre">False</span></tt>.</p>
</div></blockquote>
<p><strong>doc</strong> : str, optional</p>
<blockquote>
<div><p>A docstring describing the unit.</p>
</div></blockquote>
<p><strong>format</strong> : dict, optional</p>
<blockquote>
<div><p>A mapping to format-specific representations of this unit.
For example, for the <tt class="docutils literal"><span class="pre">Ohm</span></tt> unit, it might be nice to have it
displayed as <tt class="docutils literal"><span class="pre">\Omega</span></tt> by the <tt class="docutils literal"><span class="pre">latex</span></tt> formatter. In that
case, <tt class="xref py py-obj docutils literal"><span class="pre">format</span></tt> argument should be set to:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="p">{</span><span class="s">'latex'</span><span class="p">:</span> <span class="s">r'\Omega'</span><span class="p">}</span>
</pre></div>
</div>
</div></blockquote>
</td>
</tr>
<tr class="field-even field"><th class="field-name">Raises :</th><td class="field-body"><p class="first"><strong>ValueError</strong> :</p>
<blockquote>
<div><p>If any of the given unit names are already in the registry.</p>
</div></blockquote>
<p><strong>ValueError</strong> :</p>
<blockquote class="last">
<div><p>If any of the given unit names are not valid Python tokens.</p>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
<p class="rubric">Methods Summary</p>
<table border="1" class="longtable docutils">
<colgroup>
<col width="10%" />
<col width="90%" />
</colgroup>
<tbody valign="top">
<tr class="row-odd"><td><a class="reference internal" href="#astropy.units.core.Unit.decompose" title="astropy.units.core.Unit.decompose"><tt class="xref py py-obj docutils literal"><span class="pre">decompose</span></tt></a>([bases])</td>
<td>Return a unit object composed of only irreducible units.</td>
</tr>
</tbody>
</table>
<p class="rubric">Methods Documentation</p>
<dl class="method">
<dt id="astropy.units.core.Unit.decompose">
<tt class="descname">decompose</tt><big>(</big><em>bases=set([])</em><big>)</big><a class="reference external" href="http://github.com/astropy/astropy/tree/v0.2.4/astropy/units/core.py#L1150" title="Push the Edit button on the next page"><span class="edit-on-github viewcode-link"> [edit on github]</span></a><a class="reference internal" href="../_modules/astropy/units/core.html#Unit.decompose"><span class="viewcode-link">[source]</span></a><a class="headerlink" href="#astropy.units.core.Unit.decompose" title="Permalink to this definition">¶</a></dt>
<dd><p>Return a unit object composed of only irreducible units.</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>bases</strong> : sequence of UnitBase, optional</p>
<blockquote>
<div><p>The bases to decompose into. When not provided,
decomposes down to any irreducible units. When provided,
the decomposed result will only contain the given units.
This will raises a <a class="reference internal" href="astropy.units.core.UnitsException.html#astropy.units.core.UnitsException" title="astropy.units.core.UnitsException"><tt class="xref py py-obj docutils literal"><span class="pre">UnitsException</span></tt></a> if it’s not possible
to do so.</p>
</div></blockquote>
</td>
</tr>
<tr class="field-even field"><th class="field-name">Returns :</th><td class="field-body"><p class="first"><strong>unit</strong> : CompositeUnit object</p>
<blockquote class="last">
<div><p>New object containing only irreducible unit objects.</p>
</div></blockquote>
</td>
</tr>
</tbody>
</table>
</dd></dl>
</dd></dl>
</div>
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