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    48. 

  48.           <div class="body">
    49. 

  49.             
    50. 

  50.   <div class="section" id="standard-library">
    51. 

  51. <h1>1.2.8. Standard Library<a class="headerlink" href="#standard-library" title="Permalink to this headline"></a></h1>
    52. 

  52. <div class="admonition note">
    53. 

  53. <p class="first admonition-title">Note</p>
    54. 

  54. <p>Reference document for this section:</p>
    55. 

  55. <ul class="last simple">
    56. 

  56. <li>The Python Standard Library documentation:
    57. 

  57. <a class="reference external" href="http://docs.python.org/library/index.html">http://docs.python.org/library/index.html</a></li>
    58. 

  58. <li>Python Essential Reference, David Beazley, Addison-Wesley Professional</li>
    59. 

  59. </ul>
    60. 

  60. </div>
    61. 

  61. <div class="section" id="os-module-operating-system-functionality">
    62. 

  62. <h2>1.2.8.1. <tt class="docutils literal"><span class="pre">os</span></tt> module: operating system functionality<a class="headerlink" href="#os-module-operating-system-functionality" title="Permalink to this headline"></a></h2>
    63. 

  63. <p><em>&#8220;A portable way of using operating system dependent functionality.&#8221;</em></p>
    64. 

  64. <div class="section" id="directory-and-file-manipulation">
    65. 

  65. <h3>1.2.8.1.1. Directory and file manipulation<a class="headerlink" href="#directory-and-file-manipulation" title="Permalink to this headline"></a></h3>
    66. 

  66. <p>Current directory:</p>
    67. 

  67. <div class="highlight-ipython"><div class="highlight"><pre><span class="gp">In [17]: </span><span class="n">os</span><span class="o">.</span><span class="n">getcwd</span><span class="p">()</span>
    68. 

  68. <span class="go">Out[17]: </span><span class="s">&#39;/Users/cburns/src/scipy2009/scipy_2009_tutorial/source&#39;</span>
    69. 

  69. </pre></div>
    70. 

  70. </div>
    71. 

  71. <p>List a directory:</p>
    72. 

  72. <div class="highlight-ipython"><div class="highlight"><pre><span class="gp">In [31]: </span><span class="n">os</span><span class="o">.</span><span class="n">listdir</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">curdir</span><span class="p">)</span>
    73. 

  73. <span class="go">Out[31]:</span>
    74. 

  74. <span class="go">[&#39;.index.rst.swo&#39;,</span>
    75. 

  75. <span class="go"> &#39;.python_language.rst.swp&#39;,</span>
    76. 

  76. <span class="go"> &#39;.view_array.py.swp&#39;,</span>
    77. 

  77. <span class="go"> &#39;_static&#39;,</span>
    78. 

  78. <span class="go"> &#39;_templates&#39;,</span>
    79. 

  79. <span class="go"> &#39;basic_types.rst&#39;,</span>
    80. 

  80. <span class="go"> &#39;conf.py&#39;,</span>
    81. 

  81. <span class="go"> &#39;control_flow.rst&#39;,</span>
    82. 

  82. <span class="go"> &#39;debugging.rst&#39;,</span>
    83. 

  83. <span class="go"> ...</span>
    84. 

  84. </pre></div>
    85. 

  85. </div>
    86. 

  86. <p>Make a directory:</p>
    87. 

  87. <div class="highlight-ipython"><div class="highlight"><pre><span class="gp">In [32]: </span><span class="n">os</span><span class="o">.</span><span class="n">mkdir</span><span class="p">(</span><span class="s">&#39;junkdir&#39;</span><span class="p">)</span>
    88. 

  88. 

  89. <span class="gp">In [33]: </span><span class="s">&#39;junkdir&#39;</span> <span class="ow">in</span> <span class="n">os</span><span class="o">.</span><span class="n">listdir</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">curdir</span><span class="p">)</span>
    90. 

  90. <span class="go">Out[33]: </span><span class="bp">True</span>
    91. 

  91. </pre></div>
    92. 

  92. </div>
    93. 

  93. <p>Rename the directory:</p>
    94. 

  94. <div class="highlight-ipython"><div class="highlight"><pre><span class="gp">In [36]: </span><span class="n">os</span><span class="o">.</span><span class="n">rename</span><span class="p">(</span><span class="s">&#39;junkdir&#39;</span><span class="p">,</span> <span class="s">&#39;foodir&#39;</span><span class="p">)</span>
    95. 

  95. 

  96. <span class="gp">In [37]: </span><span class="s">&#39;junkdir&#39;</span> <span class="ow">in</span> <span class="n">os</span><span class="o">.</span><span class="n">listdir</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">curdir</span><span class="p">)</span>
    97. 

  97. <span class="go">Out[37]: </span><span class="bp">False</span>
    98. 

  98. 

  99. <span class="gp">In [38]: </span><span class="s">&#39;foodir&#39;</span> <span class="ow">in</span> <span class="n">os</span><span class="o">.</span><span class="n">listdir</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">curdir</span><span class="p">)</span>
    100. 

  100. <span class="go">Out[38]: </span><span class="bp">True</span>
    101. 

  101. 

  102. <span class="gp">In [41]: </span><span class="n">os</span><span class="o">.</span><span class="n">rmdir</span><span class="p">(</span><span class="s">&#39;foodir&#39;</span><span class="p">)</span>
    103. 

  103. 

  104. <span class="gp">In [42]: </span><span class="s">&#39;foodir&#39;</span> <span class="ow">in</span> <span class="n">os</span><span class="o">.</span><span class="n">listdir</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">curdir</span><span class="p">)</span>
    105. 

  105. <span class="go">Out[42]: </span><span class="bp">False</span>
    106. 

  106. </pre></div>
    107. 

  107. </div>
    108. 

  108. <p>Delete a file:</p>
    109. 

  109. <div class="highlight-ipython"><div class="highlight"><pre><span class="gp">In [44]: </span><span class="n">fp</span> <span class="o">=</span> <span class="nb">open</span><span class="p">(</span><span class="s">&#39;junk.txt&#39;</span><span class="p">,</span> <span class="s">&#39;w&#39;</span><span class="p">)</span>
    110. 

  110. 

  111. <span class="gp">In [45]: </span><span class="n">fp</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
    112. 

  112. 

  113. <span class="gp">In [46]: </span><span class="s">&#39;junk.txt&#39;</span> <span class="ow">in</span> <span class="n">os</span><span class="o">.</span><span class="n">listdir</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">curdir</span><span class="p">)</span>
    114. 

  114. <span class="go">Out[46]: </span><span class="bp">True</span>
    115. 

  115. 

  116. <span class="gp">In [47]: </span><span class="n">os</span><span class="o">.</span><span class="n">remove</span><span class="p">(</span><span class="s">&#39;junk.txt&#39;</span><span class="p">)</span>
    117. 

  117. 

  118. <span class="gp">In [48]: </span><span class="s">&#39;junk.txt&#39;</span> <span class="ow">in</span> <span class="n">os</span><span class="o">.</span><span class="n">listdir</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">curdir</span><span class="p">)</span>
    119. 

  119. <span class="go">Out[48]: </span><span class="bp">False</span>
    120. 

  120. </pre></div>
    121. 

  121. </div>
    122. 

  122. </div>
    123. 

  123. <div class="section" id="os-path-path-manipulations">
    124. 

  124. <h3>1.2.8.1.2. <tt class="docutils literal"><span class="pre">os.path</span></tt>: path manipulations<a class="headerlink" href="#os-path-path-manipulations" title="Permalink to this headline"></a></h3>
    125. 

  125. <p><tt class="docutils literal"><span class="pre">os.path</span></tt> provides common operations on pathnames.</p>
    126. 

  126. <div class="highlight-ipython"><div class="highlight"><pre><span class="gp">In [70]: </span><span class="n">fp</span> <span class="o">=</span> <span class="nb">open</span><span class="p">(</span><span class="s">&#39;junk.txt&#39;</span><span class="p">,</span> <span class="s">&#39;w&#39;</span><span class="p">)</span>
    127. 

  127. 

  128. <span class="gp">In [71]: </span><span class="n">fp</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
    129. 

  129. 

  130. <span class="gp">In [72]: </span><span class="n">a</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">abspath</span><span class="p">(</span><span class="s">&#39;junk.txt&#39;</span><span class="p">)</span>
    131. 

  131. 

  132. <span class="gp">In [73]: </span><span class="n">a</span>
    133. 

  133. <span class="go">Out[73]: </span><span class="s">&#39;/Users/cburns/src/scipy2009/scipy_2009_tutorial/source/junk.txt&#39;</span>
    134. 

  134. 

  135. <span class="gp">In [74]: </span><span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="n">a</span><span class="p">)</span>
    136. 

  136. <span class="go">Out[74]: </span><span class="p">(</span><span class="s">&#39;/Users/cburns/src/scipy2009/scipy_2009_tutorial/source&#39;</span><span class="p">,</span>
    137. 

  137. <span class="go">          &#39;junk.txt&#39;)</span>
    138. 

  138. 

  139. <span class="gp">In [78]: </span><span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">dirname</span><span class="p">(</span><span class="n">a</span><span class="p">)</span>
    140. 

  140. <span class="go">Out[78]: </span><span class="s">&#39;/Users/cburns/src/scipy2009/scipy_2009_tutorial/source&#39;</span>
    141. 

  141. 

  142. <span class="gp">In [79]: </span><span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">basename</span><span class="p">(</span><span class="n">a</span><span class="p">)</span>
    143. 

  143. <span class="go">Out[79]: </span><span class="s">&#39;junk.txt&#39;</span>
    144. 

  144. 

  145. <span class="gp">In [80]: </span><span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">splitext</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">basename</span><span class="p">(</span><span class="n">a</span><span class="p">))</span>
    146. 

  146. <span class="go">Out[80]: </span><span class="p">(</span><span class="s">&#39;junk&#39;</span><span class="p">,</span> <span class="s">&#39;.txt&#39;</span><span class="p">)</span>
    147. 

  147. 

  148. <span class="gp">In [84]: </span><span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">exists</span><span class="p">(</span><span class="s">&#39;junk.txt&#39;</span><span class="p">)</span>
    149. 

  149. <span class="go">Out[84]: </span><span class="bp">True</span>
    150. 

  150. 

  151. <span class="gp">In [86]: </span><span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">isfile</span><span class="p">(</span><span class="s">&#39;junk.txt&#39;</span><span class="p">)</span>
    152. 

  152. <span class="go">Out[86]: </span><span class="bp">True</span>
    153. 

  153. 

  154. <span class="gp">In [87]: </span><span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">isdir</span><span class="p">(</span><span class="s">&#39;junk.txt&#39;</span><span class="p">)</span>
    155. 

  155. <span class="go">Out[87]: </span><span class="bp">False</span>
    156. 

  156. 

  157. <span class="gp">In [88]: </span><span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">expanduser</span><span class="p">(</span><span class="s">&#39;~/local&#39;</span><span class="p">)</span>
    158. 

  158. <span class="go">Out[88]: </span><span class="s">&#39;/Users/cburns/local&#39;</span>
    159. 

  159. 

  160. <span class="gp">In [92]: </span><span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">expanduser</span><span class="p">(</span><span class="s">&#39;~&#39;</span><span class="p">),</span> <span class="s">&#39;local&#39;</span><span class="p">,</span> <span class="s">&#39;bin&#39;</span><span class="p">)</span>
    161. 

  161. <span class="go">Out[92]: </span><span class="s">&#39;/Users/cburns/local/bin&#39;</span>
    162. 

  162. </pre></div>
    163. 

  163. </div>
    164. 

  164. </div>
    165. 

  165. <div class="section" id="running-an-external-command">
    166. 

  166. <h3>1.2.8.1.3. Running an external command<a class="headerlink" href="#running-an-external-command" title="Permalink to this headline"></a></h3>
    167. 

  167. <div class="highlight-ipython"><div class="highlight"><pre><span class="gp">In [8]: </span><span class="n">os</span><span class="o">.</span><span class="n">system</span><span class="p">(</span><span class="s">&#39;ls *&#39;</span><span class="p">)</span>
    168. 

  168. <span class="go">conf.py   debug_file.py  demo2.py~  demo.py   demo.pyc          my_file.py~</span>
    169. 

  169. <span class="go">conf.py~  demo2.py     demo2.pyc  demo.py~  my_file.py  pi_wallis_image.py</span>
    170. 

  170. </pre></div>
    171. 

  171. </div>
    172. 

  172. </div>
    173. 

  173. <div class="section" id="walking-a-directory">
    174. 

  174. <h3>1.2.8.1.4. Walking a directory<a class="headerlink" href="#walking-a-directory" title="Permalink to this headline"></a></h3>
    175. 

  175. <p><tt class="docutils literal"><span class="pre">os.path.walk</span></tt> generates a list of filenames in a directory tree.</p>
    176. 

  176. <div class="highlight-ipython"><div class="highlight"><pre><span class="gp">In [10]: </span><span class="k">for</span> <span class="n">dirpath</span><span class="p">,</span> <span class="n">dirnames</span><span class="p">,</span> <span class="n">filenames</span> <span class="ow">in</span> <span class="n">os</span><span class="o">.</span><span class="n">walk</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">curdir</span><span class="p">):</span>
    177. 

  177. <span class="gp">   ....:</span>     <span class="k">for</span> <span class="n">fp</span> <span class="ow">in</span> <span class="n">filenames</span><span class="p">:</span>
    178. 

  178. <span class="gp">   ....:</span>         <span class="k">print</span> <span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">abspath</span><span class="p">(</span><span class="n">fp</span><span class="p">)</span>
    179. 

  179. <span class="gp">   ....:</span>
    180. 

  180. <span class="gp">   ....:</span>
    181. 

  181. <span class="go">/Users/cburns/src/scipy2009/scipy_2009_tutorial/source/.index.rst.swo</span>
    182. 

  182. <span class="go">/Users/cburns/src/scipy2009/scipy_2009_tutorial/source/.view_array.py.swp</span>
    183. 

  183. <span class="go">/Users/cburns/src/scipy2009/scipy_2009_tutorial/source/basic_types.rst</span>
    184. 

  184. <span class="go">/Users/cburns/src/scipy2009/scipy_2009_tutorial/source/conf.py</span>
    185. 

  185. <span class="go">/Users/cburns/src/scipy2009/scipy_2009_tutorial/source/control_flow.rst</span>
    186. 

  186. <span class="go">...</span>
    187. 

  187. </pre></div>
    188. 

  188. </div>
    189. 

  189. </div>
    190. 

  190. <div class="section" id="environment-variables">
    191. 

  191. <h3>1.2.8.1.5. Environment variables:<a class="headerlink" href="#environment-variables" title="Permalink to this headline"></a></h3>
    192. 

  192. <div class="highlight-ipython"><div class="highlight"><pre><span class="gp">In [9]: </span><span class="kn">import</span> <span class="nn">os</span>
    193. 

  193. 

  194. <span class="gp">In [11]: </span><span class="n">os</span><span class="o">.</span><span class="n">environ</span><span class="o">.</span><span class="n">keys</span><span class="p">()</span>
    195. 

  195. <span class="go">Out[11]:</span>
    196. 

  196. <span class="go">[&#39;_&#39;,</span>
    197. 

  197. <span class="go"> &#39;FSLDIR&#39;,</span>
    198. 

  198. <span class="go"> &#39;TERM_PROGRAM_VERSION&#39;,</span>
    199. 

  199. <span class="go"> &#39;FSLREMOTECALL&#39;,</span>
    200. 

  200. <span class="go"> &#39;USER&#39;,</span>
    201. 

  201. <span class="go"> &#39;HOME&#39;,</span>
    202. 

  202. <span class="go"> &#39;PATH&#39;,</span>
    203. 

  203. <span class="go"> &#39;PS1&#39;,</span>
    204. 

  204. <span class="go"> &#39;SHELL&#39;,</span>
    205. 

  205. <span class="go"> &#39;EDITOR&#39;,</span>
    206. 

  206. <span class="go"> &#39;WORKON_HOME&#39;,</span>
    207. 

  207. <span class="go"> &#39;PYTHONPATH&#39;,</span>
    208. 

  208. <span class="go"> ...</span>
    209. 

  209. 

  210. <span class="gp">In [12]: </span><span class="n">os</span><span class="o">.</span><span class="n">environ</span><span class="p">[</span><span class="s">&#39;PYTHONPATH&#39;</span><span class="p">]</span>
    211. 

  211. <span class="go">Out[12]: </span><span class="s">&#39;.:/Users/cburns/src/utils:/Users/cburns/src/nitools:</span>
    212. 

  212. <span class="go">/Users/cburns/local/lib/python2.5/site-packages/:</span>
    213. 

  213. <span class="go">/usr/local/lib/python2.5/site-packages/:</span>
    214. 

  214. <span class="go">/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5&#39;</span>
    215. 

  215. 

  216. <span class="gp">In [16]: </span><span class="n">os</span><span class="o">.</span><span class="n">getenv</span><span class="p">(</span><span class="s">&#39;PYTHONPATH&#39;</span><span class="p">)</span>
    217. 

  217. <span class="go">Out[16]: </span><span class="s">&#39;.:/Users/cburns/src/utils:/Users/cburns/src/nitools:</span>
    218. 

  218. <span class="go">/Users/cburns/local/lib/python2.5/site-packages/:</span>
    219. 

  219. <span class="go">/usr/local/lib/python2.5/site-packages/:</span>
    220. 

  220. <span class="go">/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5&#39;</span>
    221. 

  221. </pre></div>
    222. 

  222. </div>
    223. 

  223. </div>
    224. 

  224. </div>
    225. 

  225. <div class="section" id="shutil-high-level-file-operations">
    226. 

  226. <h2>1.2.8.2. <tt class="docutils literal"><span class="pre">shutil</span></tt>: high-level file operations<a class="headerlink" href="#shutil-high-level-file-operations" title="Permalink to this headline"></a></h2>
    227. 

  227. <p>The <tt class="docutils literal"><span class="pre">shutil</span></tt> provides useful file operations:</p>
    228. 

  228. <blockquote>
    229. 

  229. <ul class="simple">
    230. 

  230. <li><tt class="docutils literal"><span class="pre">shutil.rmtree</span></tt>: Recursively delete a directory tree.</li>
    231. 

  231. <li><tt class="docutils literal"><span class="pre">shutil.move</span></tt>: Recursively move a file or directory to another location.</li>
    232. 

  232. <li><tt class="docutils literal"><span class="pre">shutil.copy</span></tt>: Copy files or directories.</li>
    233. 

  233. </ul>
    234. 

  234. </blockquote>
    235. 

  235. </div>
    236. 

  236. <div class="section" id="glob-pattern-matching-on-files">
    237. 

  237. <h2>1.2.8.3. <tt class="docutils literal"><span class="pre">glob</span></tt>: Pattern matching on files<a class="headerlink" href="#glob-pattern-matching-on-files" title="Permalink to this headline"></a></h2>
    238. 

  238. <p>The <tt class="docutils literal"><span class="pre">glob</span></tt> module provides convenient file pattern matching.</p>
    239. 

  239. <p>Find all files ending in <tt class="docutils literal"><span class="pre">.txt</span></tt>:</p>
    240. 

  240. <div class="highlight-ipython"><div class="highlight"><pre><span class="gp">In [18]: </span><span class="kn">import</span> <span class="nn">glob</span>
    241. 

  241. 

  242. <span class="gp">In [19]: </span><span class="n">glob</span><span class="o">.</span><span class="n">glob</span><span class="p">(</span><span class="s">&#39;*.txt&#39;</span><span class="p">)</span>
    243. 

  243. <span class="go">Out[19]: </span><span class="p">[</span><span class="s">&#39;holy_grail.txt&#39;</span><span class="p">,</span> <span class="s">&#39;junk.txt&#39;</span><span class="p">,</span> <span class="s">&#39;newfile.txt&#39;</span><span class="p">]</span>
    244. 

  244. </pre></div>
    245. 

  245. </div>
    246. 

  246. </div>
    247. 

  247. <div class="section" id="sys-module-system-specific-information">
    248. 

  248. <h2>1.2.8.4. <tt class="docutils literal"><span class="pre">sys</span></tt> module: system-specific information<a class="headerlink" href="#sys-module-system-specific-information" title="Permalink to this headline"></a></h2>
    249. 

  249. <p>System-specific information related to the Python interpreter.</p>
    250. 

  250. <ul>
    251. 

  251. <li><p class="first">Which version of python are you running and where is it installed:</p>
    252. 

  252. <div class="highlight-ipython"><div class="highlight"><pre><span class="gp">In [117]: </span><span class="n">sys</span><span class="o">.</span><span class="n">platform</span>
    253. 

  253. <span class="go">Out[117]: </span><span class="s">&#39;darwin&#39;</span>
    254. 

  254. 

  255. <span class="gp">In [118]: </span><span class="n">sys</span><span class="o">.</span><span class="n">version</span>
    256. 

  256. <span class="go">Out[118]: </span><span class="s">&#39;2.5.2 (r252:60911, Feb 22 2008, 07:57:53) </span><span class="se">\n</span>
    257. 

  257. <span class="go">          [GCC 4.0.1 (Apple Computer, Inc. build 5363)]&#39;</span>
    258. 

  258. 

  259. <span class="gp">In [119]: </span><span class="n">sys</span><span class="o">.</span><span class="n">prefix</span>
    260. 

  260. <span class="go">Out[119]: </span><span class="s">&#39;/Library/Frameworks/Python.framework/Versions/2.5&#39;</span>
    261. 

  261. </pre></div>
    262. 

  262. </div>
    263. 

  263. </li>
    264. 

  264. <li><p class="first">List of command line arguments passed to a Python script:</p>
    265. 

  265. <div class="highlight-ipython"><div class="highlight"><pre><span class="gp">In [100]: </span><span class="n">sys</span><span class="o">.</span><span class="n">argv</span>
    266. 

  266. <span class="go">Out[100]: </span><span class="p">[</span><span class="s">&#39;/Users/cburns/local/bin/ipython&#39;</span><span class="p">]</span>
    267. 

  267. </pre></div>
    268. 

  268. </div>
    269. 

  269. </li>
    270. 

  270. </ul>
    271. 

  271. <p><tt class="docutils literal"><span class="pre">sys.path</span></tt> is a list of strings that specifies the search path for
    272. 

  272. modules.  Initialized from PYTHONPATH:</p>
    273. 

  273. <div class="highlight-ipython"><div class="highlight"><pre><span class="gp">In [121]: </span><span class="n">sys</span><span class="o">.</span><span class="n">path</span>
    274. 

  274. <span class="go">Out[121]:</span>
    275. 

  275. <span class="go">[&#39;&#39;,</span>
    276. 

  276. <span class="go"> &#39;/Users/cburns/local/bin&#39;,</span>
    277. 

  277. <span class="go"> &#39;/Users/cburns/local/lib/python2.5/site-packages/grin-1.1-py2.5.egg&#39;,</span>
    278. 

  278. <span class="go"> &#39;/Users/cburns/local/lib/python2.5/site-packages/argparse-0.8.0-py2.5.egg&#39;,</span>
    279. 

  279. <span class="go"> &#39;/Users/cburns/local/lib/python2.5/site-packages/urwid-0.9.7.1-py2.5.egg&#39;,</span>
    280. 

  280. <span class="go"> &#39;/Users/cburns/local/lib/python2.5/site-packages/yolk-0.4.1-py2.5.egg&#39;,</span>
    281. 

  281. <span class="go"> &#39;/Users/cburns/local/lib/python2.5/site-packages/virtualenv-1.2-py2.5.egg&#39;,</span>
    282. 

  282. <span class="go"> ...</span>
    283. 

  283. </pre></div>
    284. 

  284. </div>
    285. 

  285. </div>
    286. 

  286. <div class="section" id="pickle-easy-persistence">
    287. 

  287. <h2>1.2.8.5. <tt class="docutils literal"><span class="pre">pickle</span></tt>: easy persistence<a class="headerlink" href="#pickle-easy-persistence" title="Permalink to this headline"></a></h2>
    288. 

  288. <p>Useful to store arbitrary objects to a file. Not safe or fast!</p>
    289. 

  289. <div class="highlight-ipython"><div class="highlight"><pre><span class="gp">In [1]: </span><span class="kn">import</span> <span class="nn">pickle</span>
    290. 

  290. 

  291. <span class="gp">In [2]: </span><span class="n">l</span> <span class="o">=</span> <span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="bp">None</span><span class="p">,</span> <span class="s">&#39;Stan&#39;</span><span class="p">]</span>
    292. 

  292. 

  293. <span class="gp">In [3]: </span><span class="n">pickle</span><span class="o">.</span><span class="n">dump</span><span class="p">(</span><span class="n">l</span><span class="p">,</span> <span class="nb">file</span><span class="p">(</span><span class="s">&#39;test.pkl&#39;</span><span class="p">,</span> <span class="s">&#39;w&#39;</span><span class="p">))</span>
    294. 

  294. 

  295. <span class="gp">In [4]: </span><span class="n">pickle</span><span class="o">.</span><span class="n">load</span><span class="p">(</span><span class="nb">file</span><span class="p">(</span><span class="s">&#39;test.pkl&#39;</span><span class="p">))</span>
    296. 

  296. <span class="go">Out[4]: </span><span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="bp">None</span><span class="p">,</span> <span class="s">&#39;Stan&#39;</span><span class="p">]</span>
    297. 

  297. </pre></div>
    298. 

  298. </div>
    299. 

  299. <div class="topic">
    300. 

  300. <p class="topic-title first">Exercise</p>
    301. 

  301. <p>Write a program to search your PYTHONPATH for the module <tt class="docutils literal"><span class="pre">site.py</span></tt>.</p>
    302. 

  302. </div>
    303. 

  303. <p><a class="reference internal" href="../solutions.html#path-site"><em>The PYTHONPATH Search Solution</em></a></p>
    304. 

  304. </div>
    305. 

  305. </div>
    306. 

  306. 

  307. 

  308.           </div>
    309. 

  309.       </div>
    310. 

  310.       <div class="clearer"></div>
    311. 

  311.     </div>
    312. 

  312.     <div class="related">
    313. 

  313.       <h3>Navigation</h3>
    314. 

  314.       <ul>
    315. 

  315.         <li class="right" style="margin-right: 10px">
    316. 

  316.           <a href="exceptions.html" title="1.2.9. Exceptions handling in Python"
    317. 

  317.              >next</a></li>
    318. 

  318.         <li class="right" >
    319. 

  319.           <a href="io.html" title="1.2.7. Input and Output"
    320. 

  320.              >previous</a> |</li>
    321. 

  321.         <li><a href="../../index.html">Scipy lecture notes</a> &raquo;</li>
    322. 

  322.           <li><a href="../index.html" >1. Getting started with Python for science</a> &raquo;</li>
    323. 

  323.           <li><a href="python_language.html" >1.2. The Python language</a> &raquo;</li> 
    324. 

  324.       </ul>
    325. 

  325.     </div>
    326. 

  326.     <div class="footer">
    327. 

  327.         &copy; Copyright 2011.
    328. 

  328.       Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 1.0.
    329. 

  329.     </div>
    330. 

  330.   </body>
    331. 

  331. </html>
    332.