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<div class="section" id="creating-coordinate-objects">
<h1>Creating Coordinate Objects<a class="headerlink" href="#creating-coordinate-objects" title="Permalink to this headline">ΒΆ</a></h1>
<p>Creating new coordinate objects is of course crucial to using
<a class="reference internal" href="index.html#module-astropy.coordinates" title="astropy.coordinates"><tt class="xref py py-obj docutils literal"><span class="pre">coordinates</span></tt></a>. The typical way to create a new coordinate object
is to directly initialize your preferred coordinate system using standard
python class creation, using the name of the class representing that
system and a number for the two angles. For example:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">astropy.coordinates</span> <span class="kn">import</span> <span class="n">ICRSCoordinates</span><span class="p">,</span> <span class="n">FK4Coordinates</span><span class="p">,</span> <span class="n">GalacticCoordinates</span>
<span class="gp">>>> </span><span class="n">ICRSCoordinates</span><span class="p">(</span><span class="mf">187.70592</span><span class="p">,</span> <span class="mf">12.39112</span><span class="p">,</span> <span class="n">unit</span><span class="o">=</span><span class="p">(</span><span class="n">u</span><span class="o">.</span><span class="n">degree</span><span class="p">,</span> <span class="n">u</span><span class="o">.</span><span class="n">degree</span><span class="p">))</span>
<span class="go"><ICRSCoordinates RA=187.70592 deg, Dec=12.39112 deg></span>
<span class="gp">>>> </span><span class="n">FK4Coordinates</span><span class="p">(</span><span class="mf">187.07317</span><span class="p">,</span> <span class="mf">12.66715</span><span class="p">,</span> <span class="n">unit</span><span class="o">=</span><span class="p">(</span><span class="n">u</span><span class="o">.</span><span class="n">degree</span><span class="p">,</span> <span class="n">u</span><span class="o">.</span><span class="n">degree</span><span class="p">))</span>
<span class="go"><FK4Coordinates RA=187.07317 deg, Dec=12.66715 deg></span>
<span class="gp">>>> </span><span class="n">GalacticCoordinates</span><span class="p">(</span><span class="o">-</span><span class="mf">76.22237</span><span class="p">,</span> <span class="mf">74.49108</span><span class="p">,</span> <span class="n">unit</span><span class="o">=</span><span class="p">(</span><span class="n">u</span><span class="o">.</span><span class="n">degree</span><span class="p">,</span> <span class="n">u</span><span class="o">.</span><span class="n">degree</span><span class="p">))</span>
<span class="go"><GalacticCoordinates l=-76.22237 deg, b=74.49108 deg></span>
</pre></div>
</div>
<p>Note that if you do not provide units explicitly, this will fail:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">ICRSCoordinates</span><span class="p">(</span><span class="mi">23</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span>
<span class="go">UnitsError: No unit was specified in Angle initializer; the unit parameter should be an object from the astropy.units module (e.g. 'from astropy import units as u', then use 'u.degree').</span>
</pre></div>
</div>
<p>While the above example uses python numerical types, you can also provide strings to create coordinates.
If the <tt class="xref py py-obj docutils literal"><span class="pre">unit</span></tt> parameter is <tt class="docutils literal"><span class="pre">(None,</span> <span class="pre">None)</span></tt> (the default), strings will be interpreted using the <tt class="xref py py-obj docutils literal"><span class="pre">Angle</span></tt>
class’ parsing scheme, and has a guiding principal of being able to interpret any <em>unambiguous</em> string
specifying an angle. For the exact rules for how each string is parsed, see the
<a class="reference internal" href="../_generated/astropy.coordinates.angles.Angle.html#astropy.coordinates.angles.Angle" title="astropy.coordinates.angles.Angle"><tt class="xref py py-obj docutils literal"><span class="pre">Angle</span></tt></a> documentation. Some examples:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">ICRSCoordinates</span><span class="p">(</span><span class="s">"3h36m29.7888s -41d08m15.162342s"</span><span class="p">,</span> <span class="n">unit</span><span class="o">=</span><span class="p">(</span><span class="bp">None</span><span class="p">,</span> <span class="bp">None</span><span class="p">))</span>
<span class="go"><ICRSCoordinates RA=54.12412 deg, Dec=-41.13755 deg></span>
<span class="gp">>>> </span><span class="n">ICRSCoordinates</span><span class="p">(</span><span class="s">"3h36m29.7888s -41d08m15.162342s"</span><span class="p">)</span>
<span class="go"><ICRSCoordinates RA=54.12412 deg, Dec=-41.13755 deg></span>
<span class="gp">>>> </span><span class="n">ICRSCoordinates</span><span class="p">(</span><span class="s">"14.12412 hours"</span><span class="p">,</span> <span class="s">"-41:08:15.162342 degrees"</span><span class="p">)</span>
<span class="go"><ICRSCoordinates RA=211.86180 deg, Dec=-41.13755 deg></span>
<span class="gp">>>> </span><span class="n">ICRSCoordinates</span><span class="p">(</span><span class="s">"14.12412 -41:08:15.162342"</span><span class="p">)</span>
<span class="go">UnitsError: Could not infer Angle units from provided string 14.12412</span>
</pre></div>
</div>
<p>You can also directly specify the units for both to resolve ambiguities in parsing the angle strings:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">ICRSCoordinates</span><span class="p">(</span><span class="s">"14.12412 -41:08:15.162342"</span><span class="p">,</span> <span class="n">unit</span><span class="o">=</span><span class="p">(</span><span class="n">u</span><span class="o">.</span><span class="n">hour</span><span class="p">,</span> <span class="n">u</span><span class="o">.</span><span class="n">degree</span><span class="p">))</span>
<span class="go"><ICRSCoordinates RA=211.86180 deg, Dec=-41.13755 deg></span>
<span class="gp">>>> </span><span class="n">ICRSCoordinates</span><span class="p">(</span><span class="s">"54:7:26.832 -41:08:15.162342"</span><span class="p">,</span> <span class="n">unit</span><span class="o">=</span><span class="p">(</span><span class="n">u</span><span class="o">.</span><span class="n">degree</span><span class="p">,</span> <span class="n">u</span><span class="o">.</span><span class="n">degree</span><span class="p">))</span>
<span class="go"><ICRSCoordinates RA=54.12412 deg, Dec=-41.13755 deg></span>
<span class="gp">>>> </span><span class="n">ICRSCoordinates</span><span class="p">(</span><span class="s">'3 4 5 +6 7 8'</span><span class="p">,</span> <span class="n">unit</span><span class="o">=</span><span class="p">(</span><span class="n">u</span><span class="o">.</span><span class="n">hour</span><span class="p">,</span> <span class="n">u</span><span class="o">.</span><span class="n">degree</span><span class="p">))</span>
<span class="go"><ICRSCoordinates RA=46.02083 deg, Dec=6.11889 deg></span>
<span class="gp">>>> </span><span class="n">ICRSCoordinates</span><span class="p">(</span><span class="s">'3h4m5s +6d7m8s'</span><span class="p">,</span> <span class="n">unit</span><span class="o">=</span><span class="p">(</span><span class="n">u</span><span class="o">.</span><span class="n">hour</span><span class="p">,</span> <span class="n">u</span><span class="o">.</span><span class="n">degree</span><span class="p">))</span>
<span class="go"><ICRSCoordinates RA=46.02083 deg, Dec=6.11889 deg></span>
</pre></div>
</div>
<p>This will also give you an error if you give a string with units that conflict with your desired units:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">ICRSCoordinates</span><span class="p">(</span><span class="s">'3d4m5s +6h7m8s'</span><span class="p">,</span> <span class="n">unit</span><span class="o">=</span><span class="p">(</span><span class="n">u</span><span class="o">.</span><span class="n">hour</span><span class="p">,</span> <span class="n">u</span><span class="o">.</span><span class="n">degree</span><span class="p">))</span>
<span class="go">ValueError: parse_hours: Invalid input string, can't parse to HMS. (3d4m5s)</span>
</pre></div>
</div>
<p>One final way to create coordinates is to copy them from an already existing coordinate:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">i1</span> <span class="o">=</span> <span class="n">ICRSCoordinates</span><span class="p">(</span><span class="mf">187.70592</span><span class="p">,</span> <span class="mf">12.39112</span><span class="p">,</span> <span class="n">unit</span><span class="o">=</span><span class="p">(</span><span class="n">u</span><span class="o">.</span><span class="n">degree</span><span class="p">,</span> <span class="n">u</span><span class="o">.</span><span class="n">degree</span><span class="p">))</span>
<span class="gp">>>> </span><span class="n">i2</span> <span class="o">=</span> <span class="n">ICRSCoordinates</span><span class="p">(</span><span class="n">i1</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">i1</span>
<span class="go"><ICRSCoordinates RA=187.70592 deg, Dec=12.39112 deg></span>
<span class="gp">>>> </span><span class="n">i2</span>
<span class="go"><ICRSCoordinates RA=187.70592 deg, Dec=12.39112 deg></span>
</pre></div>
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