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	<div class="section" id="the-io-module">
	<h1>the Io module<a class="headerlink" href="#the-io-module" title="Permalink to this headline">¶</a></h1>
	<dl class="function">
	<dt id="pNbody.io.checkfile">
	<tt class="descclassname">pNbody.io.</tt><tt class="descname">checkfile</tt><big>(</big><em>name</em><big>)</big><a class="headerlink" href="#pNbody.io.checkfile" title="Permalink to this definition">¶</a></dt>
	<dd><p>Check if a file exists. An error is generated if the file
	does not exists.</p>
	<table class="docutils field-list" frame="void" rules="none">
	<col class="field-name" />
	<col class="field-body" />
	<tbody valign="top">
	<tr class="field"><th class="field-name">Parameters :</th><td class="field-body"><strong>name</strong> : the path to a filename</td>
	</tr>
	</tbody>
	</table>
	<p class="rubric">Examples</p>
	<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">io</span><span class="o">.</span><span class="n">checkfile</span><span class="p">(</span><span class="s">'an_existing_file'</span><span class="p">)</span>
	<span class="gp">>>> </span>
	</pre></div>
	</div>
	<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">io</span><span class="o">.</span><span class="n">checkfile</span><span class="p">(</span><span class="s">'a_non_existing_file'</span><span class="p">)</span>
	<span class="gt">Traceback (most recent call last):</span>
	File <span class="nb">"<stdin>"</span>, line <span class="m">1</span>, in <span class="n-Identifier"><module></span>
	File <span class="nb">"/home/epfl/revaz/local/lib64/python2.6/site-packages/pNbody/io.py"</span>, line <span class="m">33</span>, in <span class="n-Identifier">checkfile</span>
	<span class="k">raise</span> <span class="ne">IOError</span><span class="p">(</span><span class="mi">915</span><span class="p">,</span><span class="s">'file </span><span class="si">%s</span><span class="s"> not found ! Pease check the file name.'</span><span class="o">%</span><span class="p">(</span><span class="n">name</span><span class="p">))</span>
	<span class="nc">IOError</span>: <span class="n-Identifier">[Errno 915] file nofile not found ! Pease check the file name. </span>
	</pre></div>
	</div>
	</dd></dl>

	<dl class="function">
	<dt id="pNbody.io.end_of_file">
	<tt class="descclassname">pNbody.io.</tt><tt class="descname">end_of_file</tt><big>(</big><em>f</em>, <em>pio='no'</em>, <em>MPI=None</em><big>)</big><a class="headerlink" href="#pNbody.io.end_of_file" title="Permalink to this definition">¶</a></dt>
	<dd><p>Return True if we have reached the end of the file f, False instead</p>
	<table class="docutils field-list" frame="void" rules="none">
	<col class="field-name" />
	<col class="field-body" />
	<tbody valign="top">
	<tr class="field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>f</strong> : ndarray or matrix object</p>
	<blockquote>
	<p>an open file</p>
	</blockquote>
	<p><strong>pio</strong> : ‘yes’ or ‘no’</p>
	<blockquote>
	<p>if the file is read in parallel or not</p>
	</blockquote>
	<p><strong>MPI</strong> : MPI communicator</p>
	</td>
	</tr>
	<tr class="field"><th class="field-name">Returns :</th><td class="field-body"><p class="first"><strong>status</strong> : Bool</p>
	<blockquote class="last">
	<p>True if the we reached the end of the file
	False if not</p>
	</blockquote>
	</td>
	</tr>
	</tbody>
	</table>
	</dd></dl>

	<dl class="function">
	<dt id="pNbody.io.write_array">
	<tt class="descclassname">pNbody.io.</tt><tt class="descname">write_array</tt><big>(</big><em>file</em>, <em>vec</em><big>)</big><a class="headerlink" href="#pNbody.io.write_array" title="Permalink to this definition">¶</a></dt>
	<dd><p>Write an array to a file, in a very simple ascii format.</p>
	<table class="docutils field-list" frame="void" rules="none">
	<col class="field-name" />
	<col class="field-body" />
	<tbody valign="top">
	<tr class="field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>file</strong> : the path to a file</p>
	<p class="last"><strong>vec</strong> : an ndarray object</p>
	</td>
	</tr>
	</tbody>
	</table>
	<p class="rubric">Examples</p>
	<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">numpy</span> <span class="kn">import</span> <span class="o">*</span>
	<span class="gp">>>> </span><span class="n">x</span> <span class="o">=</span> <span class="n">array</span><span class="p">([</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">])</span>
	<span class="gp">>>> </span><span class="n">io</span><span class="o">.</span><span class="n">write_array</span><span class="p">(</span><span class="s">'/tmp/array.dat'</span><span class="p">,</span><span class="n">x</span><span class="p">)</span>
	</pre></div>
	</div>
	</dd></dl>

	<dl class="function">
	<dt id="pNbody.io.read_ascii">
	<tt class="descclassname">pNbody.io.</tt><tt class="descname">read_ascii</tt><big>(</big><em>file</em>, <em>columns=None</em>, <em>lines=None</em>, <em>dtype=<type 'float'></em>, <em>skipheader=False</em>, <em>cchar='#'</em><big>)</big><a class="headerlink" href="#pNbody.io.read_ascii" title="Permalink to this definition">¶</a></dt>
	<dd><p>Read an ascii file.
	The function allows to set the number of columns or line to read.
	If it contains a header, the header is used to label all column. In
	this case, a dictionary is returned.</p>
	<table class="docutils field-list" frame="void" rules="none">
	<col class="field-name" />
	<col class="field-body" />
	<tbody valign="top">
	<tr class="field"><th class="field-name">Parameters :</th><td class="field-body"><p class="first"><strong>file</strong> : the path to a file or an open file</p>
	<p><strong>columns</strong> : list</p>
	<blockquote>
	<p>the list of the columns to read
	if none, all columns are read</p>
	</blockquote>
	<p><strong>lines</strong> : list</p>
	<blockquote>
	<p>the list of the lines to read
	if none, all lines are read</p>
	</blockquote>
	<p><strong>dtype</strong> : dtype</p>
	<blockquote>
	<p>the ndtype of the objects to read</p>
	</blockquote>
	<p><strong>skipheader</strong> : bool</p>
	<blockquote>
	<p>if true, do not read the header
	if there is one</p>
	</blockquote>
	<p><strong>cchar</strong> : char</p>
	<blockquote>
	<p>lines begining with cchar are skiped
	the first line is considered as the header</p>
	</blockquote>
	</td>
	</tr>
	<tr class="field"><th class="field-name">Returns :</th><td class="field-body"><p class="first"><strong>data</strong> : Dict or ndarray</p>
	<blockquote class="last">
	<p>A python dictionary or an ndarray object</p>
	</blockquote>
	</td>
	</tr>
	</tbody>
	</table>
	<p class="rubric">Examples</p>
	<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">numpy</span> <span class="kn">import</span> <span class="o">*</span>
	<span class="gp">>>> </span><span class="n">x</span> <span class="o">=</span> <span class="n">arange</span><span class="p">(</span><span class="mi">10</span><span class="p">)</span>
	<span class="gp">>>> </span><span class="n">y</span> <span class="o">=</span> <span class="n">x</span><span class="o">*</span><span class="n">x</span>
	<span class="gp">>>> </span><span class="n">f</span> <span class="o">=</span> <span class="nb">open</span><span class="p">(</span><span class="s">'afile.txt'</span><span class="p">,</span><span class="s">'w'</span><span class="p">)</span>
	<span class="gp">>>> </span><span class="n">f</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s">"# x y"</span><span class="p">)</span>
	<span class="gp">>>> </span><span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">xrange</span><span class="p">(</span><span class="nb">len</span><span class="p">(</span><span class="n">x</span><span class="p">)):</span>
	<span class="gp">... </span> <span class="n">f</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s">'</span><span class="si">%g</span><span class="s"> </span><span class="si">%g</span><span class="s">'</span><span class="o">%</span><span class="p">(</span><span class="n">x</span><span class="p">[</span><span class="n">i</span><span class="p">],</span><span class="n">y</span><span class="p">[</span><span class="n">i</span><span class="p">]))</span>
	<span class="gp">... </span>
	<span class="gp">>>> </span><span class="n">f</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
	<span class="gp">>>> </span><span class="kn">from</span> <span class="nn">pNbody</span> <span class="kn">import</span> <span class="n">io</span>
	<span class="gp">>>> </span><span class="n">data</span> <span class="o">=</span> <span class="n">io</span><span class="o">.</span><span class="n">read_ascii</span><span class="p">(</span><span class="s">"afile.txt"</span><span class="p">)</span>
	<span class="gp">>>> </span><span class="n">data</span><span class="p">[</span><span class="s">'x'</span><span class="p">]</span>
	<span class="go">array([ 0., 1., 2., 3., 4., 5., 6., 7., 8., 9.])</span>
	<span class="gp">>>> </span><span class="n">data</span><span class="p">[</span><span class="s">'y'</span><span class="p">]</span>
	<span class="go">array([ 0., 1., 4., 9., 16., 25., 36., 49., 64., 81.]) </span>
	</pre></div>
	</div>
	</dd></dl>

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