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<h1>Source code for networkx.utils.decorators</h1><div class="highlight"><pre>
<span class="kn">import</span> <span class="nn">sys</span>
<span class="kn">from</span> <span class="nn">collections</span> <span class="kn">import</span> <span class="n">defaultdict</span>
<span class="kn">from</span> <span class="nn">os.path</span> <span class="kn">import</span> <span class="n">splitext</span>
<span class="kn">import</span> <span class="nn">networkx</span> <span class="kn">as</span> <span class="nn">nx</span>
<span class="kn">from</span> <span class="nn">decorator</span> <span class="kn">import</span> <span class="n">decorator</span>
<span class="kn">from</span> <span class="nn">networkx.utils</span> <span class="kn">import</span> <span class="n">is_string_like</span>
<span class="k">def</span> <span class="nf">not_implemented_for</span><span class="p">(</span><span class="o">*</span><span class="n">graph_types</span><span class="p">):</span>
<span class="sd">"""Decorator to mark algorithms as not implemented</span>
<span class="sd"> Parameters</span>
<span class="sd"> ----------</span>
<span class="sd"> graph_types : container of strings</span>
<span class="sd"> Entries must be one of 'directed','undirected', 'multigraph', 'graph'.</span>
<span class="sd"> Returns</span>
<span class="sd"> -------</span>
<span class="sd"> _require : function</span>
<span class="sd"> The decorated function.</span>
<span class="sd"> Raises</span>
<span class="sd"> ------</span>
<span class="sd"> NetworkXNotImplemnted</span>
<span class="sd"> If any of the packages cannot be imported</span>
<span class="sd"> Notes</span>
<span class="sd"> -----</span>
<span class="sd"> Multiple types are joined logically with "and".</span>
<span class="sd"> For "or" use multiple @not_implemented_for() lines.</span>
<span class="sd"> Examples</span>
<span class="sd"> --------</span>
<span class="sd"> Decorate functions like this::</span>
<span class="sd"> @not_implemnted_for('directed')</span>
<span class="sd"> def sp_function():</span>
<span class="sd"> pass</span>
<span class="sd"> @not_implemnted_for('directed','multigraph')</span>
<span class="sd"> def sp_np_function():</span>
<span class="sd"> pass</span>
<span class="sd"> """</span>
<span class="nd">@decorator</span>
<span class="k">def</span> <span class="nf">_not_implemented_for</span><span class="p">(</span><span class="n">f</span><span class="p">,</span><span class="o">*</span><span class="n">args</span><span class="p">,</span><span class="o">**</span><span class="n">kwargs</span><span class="p">):</span>
<span class="n">graph</span> <span class="o">=</span> <span class="n">args</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>
<span class="n">terms</span><span class="o">=</span> <span class="p">{</span><span class="s">'directed'</span><span class="p">:</span><span class="n">graph</span><span class="o">.</span><span class="n">is_directed</span><span class="p">(),</span>
<span class="s">'undirected'</span><span class="p">:</span><span class="ow">not</span> <span class="n">graph</span><span class="o">.</span><span class="n">is_directed</span><span class="p">(),</span>
<span class="s">'multigraph'</span><span class="p">:</span><span class="n">graph</span><span class="o">.</span><span class="n">is_multigraph</span><span class="p">(),</span>
<span class="s">'graph'</span><span class="p">:</span><span class="ow">not</span> <span class="n">graph</span><span class="o">.</span><span class="n">is_multigraph</span><span class="p">()}</span>
<span class="n">match</span> <span class="o">=</span> <span class="bp">True</span>
<span class="k">try</span><span class="p">:</span>
<span class="k">for</span> <span class="n">t</span> <span class="ow">in</span> <span class="n">graph_types</span><span class="p">:</span>
<span class="n">match</span> <span class="o">=</span> <span class="n">match</span> <span class="ow">and</span> <span class="n">terms</span><span class="p">[</span><span class="n">t</span><span class="p">]</span>
<span class="k">except</span> <span class="ne">KeyError</span><span class="p">:</span>
<span class="k">raise</span> <span class="ne">KeyError</span><span class="p">(</span><span class="s">'use one or more of '</span><span class="p">,</span>
<span class="s">'directed, undirected, multigraph, graph'</span><span class="p">)</span>
<span class="k">if</span> <span class="n">match</span><span class="p">:</span>
<span class="k">raise</span> <span class="n">nx</span><span class="o">.</span><span class="n">NetworkXNotImplemented</span><span class="p">(</span><span class="s">'not implemented for </span><span class="si">%s</span><span class="s"> type'</span><span class="o">%</span>
<span class="s">' '</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">graph_types</span><span class="p">))</span>
<span class="k">else</span><span class="p">:</span>
<span class="k">return</span> <span class="n">f</span><span class="p">(</span><span class="o">*</span><span class="n">args</span><span class="p">,</span><span class="o">**</span><span class="n">kwargs</span><span class="p">)</span>
<span class="k">return</span> <span class="n">_not_implemented_for</span>
<div class="viewcode-block" id="require"><a class="viewcode-back" href="../../../reference/generated/networkx.utils.decorators.require.html#networkx.utils.decorators.require">[docs]</a><span class="k">def</span> <span class="nf">require</span><span class="p">(</span><span class="o">*</span><span class="n">packages</span><span class="p">):</span>
<span class="sd">"""Decorator to check whether specific packages can be imported.</span>
<span class="sd"> If a package cannot be imported, then NetworkXError is raised.</span>
<span class="sd"> If all packages can be imported, then the original function is called.</span>
<span class="sd"> Parameters</span>
<span class="sd"> ----------</span>
<span class="sd"> packages : container of strings</span>
<span class="sd"> Container of module names that will be imported.</span>
<span class="sd"> Returns</span>
<span class="sd"> -------</span>
<span class="sd"> _require : function</span>
<span class="sd"> The decorated function.</span>
<span class="sd"> Raises</span>
<span class="sd"> ------</span>
<span class="sd"> NetworkXError</span>
<span class="sd"> If any of the packages cannot be imported</span>
<span class="sd"> Examples</span>
<span class="sd"> --------</span>
<span class="sd"> Decorate functions like this::</span>
<span class="sd"> @require('scipy')</span>
<span class="sd"> def sp_function():</span>
<span class="sd"> import scipy</span>
<span class="sd"> pass</span>
<span class="sd"> @require('numpy','scipy')</span>
<span class="sd"> def sp_np_function():</span>
<span class="sd"> import numpy</span>
<span class="sd"> import scipy</span>
<span class="sd"> pass</span>
<span class="sd"> """</span>
<span class="nd">@decorator</span>
<span class="k">def</span> <span class="nf">_require</span><span class="p">(</span><span class="n">f</span><span class="p">,</span><span class="o">*</span><span class="n">args</span><span class="p">,</span><span class="o">**</span><span class="n">kwargs</span><span class="p">):</span>
<span class="k">for</span> <span class="n">package</span> <span class="ow">in</span> <span class="nb">reversed</span><span class="p">(</span><span class="n">packages</span><span class="p">):</span>
<span class="k">try</span><span class="p">:</span>
<span class="nb">__import__</span><span class="p">(</span><span class="n">package</span><span class="p">)</span>
<span class="k">except</span><span class="p">:</span>
<span class="n">msg</span> <span class="o">=</span> <span class="s">"{0} requires {1}"</span>
<span class="k">raise</span> <span class="n">nx</span><span class="o">.</span><span class="n">NetworkXError</span><span class="p">(</span> <span class="n">msg</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">f</span><span class="o">.</span><span class="n">__name__</span><span class="p">,</span> <span class="n">package</span><span class="p">)</span> <span class="p">)</span>
<span class="k">return</span> <span class="n">f</span><span class="p">(</span><span class="o">*</span><span class="n">args</span><span class="p">,</span><span class="o">**</span><span class="n">kwargs</span><span class="p">)</span>
<span class="k">return</span> <span class="n">_require</span>
</div>
<span class="k">def</span> <span class="nf">_open_gz</span><span class="p">(</span><span class="n">path</span><span class="p">,</span> <span class="n">mode</span><span class="p">):</span>
<span class="kn">import</span> <span class="nn">gzip</span>
<span class="k">return</span> <span class="n">gzip</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="n">path</span><span class="p">,</span><span class="n">mode</span><span class="o">=</span><span class="n">mode</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">_open_bz2</span><span class="p">(</span><span class="n">path</span><span class="p">,</span> <span class="n">mode</span><span class="p">):</span>
<span class="kn">import</span> <span class="nn">bz2</span>
<span class="k">return</span> <span class="n">bz2</span><span class="o">.</span><span class="n">BZ2File</span><span class="p">(</span><span class="n">path</span><span class="p">,</span><span class="n">mode</span><span class="o">=</span><span class="n">mode</span><span class="p">)</span>
<span class="c"># To handle new extensions, define a function accepting a `path` and `mode`.</span>
<span class="c"># Then add the extension to _dispatch_dict.</span>
<span class="n">_dispatch_dict</span> <span class="o">=</span> <span class="n">defaultdict</span><span class="p">(</span><span class="k">lambda</span> <span class="p">:</span> <span class="nb">open</span><span class="p">)</span>
<span class="n">_dispatch_dict</span><span class="p">[</span><span class="s">'.gz'</span><span class="p">]</span> <span class="o">=</span> <span class="n">_open_gz</span>
<span class="n">_dispatch_dict</span><span class="p">[</span><span class="s">'.bz2'</span><span class="p">]</span> <span class="o">=</span> <span class="n">_open_bz2</span>
<span class="n">_dispatch_dict</span><span class="p">[</span><span class="s">'.gzip'</span><span class="p">]</span> <span class="o">=</span> <span class="n">_open_gz</span>
<div class="viewcode-block" id="open_file"><a class="viewcode-back" href="../../../reference/generated/networkx.utils.decorators.open_file.html#networkx.utils.decorators.open_file">[docs]</a><span class="k">def</span> <span class="nf">open_file</span><span class="p">(</span><span class="n">path_arg</span><span class="p">,</span> <span class="n">mode</span><span class="o">=</span><span class="s">'r'</span><span class="p">):</span>
<span class="sd">"""Decorator to ensure clean opening and closing of files.</span>
<span class="sd"> Parameters</span>
<span class="sd"> ----------</span>
<span class="sd"> path_arg : int</span>
<span class="sd"> Location of the path argument in args. Even if the argument is a</span>
<span class="sd"> named positional argument (with a default value), you must specify its</span>
<span class="sd"> index as a positional argument.</span>
<span class="sd"> mode : str</span>
<span class="sd"> String for opening mode.</span>
<span class="sd"> Returns</span>
<span class="sd"> -------</span>
<span class="sd"> _open_file : function</span>
<span class="sd"> Function which cleanly executes the io.</span>
<span class="sd"> Examples</span>
<span class="sd"> --------</span>
<span class="sd"> Decorate functions like this::</span>
<span class="sd"> @open_file(0,'r')</span>
<span class="sd"> def read_function(pathname):</span>
<span class="sd"> pass</span>
<span class="sd"> @open_file(1,'w')</span>
<span class="sd"> def write_function(G,pathname):</span>
<span class="sd"> pass</span>
<span class="sd"> @open_file(1,'w')</span>
<span class="sd"> def write_function(G, pathname='graph.dot')</span>
<span class="sd"> pass</span>
<span class="sd"> @open_file('path', 'w+')</span>
<span class="sd"> def another_function(arg, **kwargs):</span>
<span class="sd"> path = kwargs['path']</span>
<span class="sd"> pass</span>
<span class="sd"> """</span>
<span class="c"># Note that this decorator solves the problem when a path argument is</span>
<span class="c"># specified as a string, but it does not handle the situation when the</span>
<span class="c"># function wants to accept a default of None (and then handle it).</span>
<span class="c"># Here is an example:</span>
<span class="c">#</span>
<span class="c"># @open_file('path')</span>
<span class="c"># def some_function(arg1, arg2, path=None):</span>
<span class="c"># if path is None:</span>
<span class="c"># fobj = tempfile.NamedTemporaryFile(delete=False)</span>
<span class="c"># close_fobj = True</span>
<span class="c"># else:</span>
<span class="c"># # `path` could have been a string or file object or something</span>
<span class="c"># # similar. In any event, the decorator has given us a file object</span>
<span class="c"># # and it will close it for us, if it should.</span>
<span class="c"># fobj = path</span>
<span class="c"># close_fobj = False</span>
<span class="c">#</span>
<span class="c"># try:</span>
<span class="c"># fobj.write('blah')</span>
<span class="c"># finally:</span>
<span class="c"># if close_fobj:</span>
<span class="c"># fobj.close()</span>
<span class="c">#</span>
<span class="c"># Normally, we'd want to use "with" to ensure that fobj gets closed.</span>
<span class="c"># However, recall that the decorator will make `path` a file object for</span>
<span class="c"># us, and using "with" would undesirably close that file object. Instead,</span>
<span class="c"># you use a try block, as shown above. When we exit the function, fobj will</span>
<span class="c"># be closed, if it should be, by the decorator.</span>
<span class="nd">@decorator</span>
<span class="k">def</span> <span class="nf">_open_file</span><span class="p">(</span><span class="n">func</span><span class="p">,</span> <span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">):</span>
<span class="c"># Note that since we have used @decorator, *args, and **kwargs have</span>
<span class="c"># already been resolved to match the function signature of func. This</span>
<span class="c"># means default values have been propagated. For example, the function</span>
<span class="c"># func(x, y, a=1, b=2, **kwargs) if called as func(0,1,b=5,c=10) would</span>
<span class="c"># have args=(0,1,1,5) and kwargs={'c':10}.</span>
<span class="c"># First we parse the arguments of the decorator. The path_arg could</span>
<span class="c"># be an positional argument or a keyword argument. Even if it is</span>
<span class="k">try</span><span class="p">:</span>
<span class="c"># path_arg is a required positional argument</span>
<span class="c"># This works precisely because we are using @decorator</span>
<span class="n">path</span> <span class="o">=</span> <span class="n">args</span><span class="p">[</span><span class="n">path_arg</span><span class="p">]</span>
<span class="k">except</span> <span class="ne">TypeError</span><span class="p">:</span>
<span class="c"># path_arg is a keyword argument. It is "required" in the sense</span>
<span class="c"># that it must exist, according to the decorator specification,</span>
<span class="c"># It can exist in `kwargs` by a developer specified default value</span>
<span class="c"># or it could have been explicitly set by the user.</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">path</span> <span class="o">=</span> <span class="n">kwargs</span><span class="p">[</span><span class="n">path_arg</span><span class="p">]</span>
<span class="k">except</span> <span class="ne">KeyError</span><span class="p">:</span>
<span class="c"># Could not find the keyword. Thus, no default was specified</span>
<span class="c"># in the function signature and the user did not provide it.</span>
<span class="n">msg</span> <span class="o">=</span> <span class="s">'Missing required keyword argument: {0}'</span>
<span class="k">raise</span> <span class="n">nx</span><span class="o">.</span><span class="n">NetworkXError</span><span class="p">(</span><span class="n">msg</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">path_arg</span><span class="p">))</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">is_kwarg</span> <span class="o">=</span> <span class="bp">True</span>
<span class="k">except</span> <span class="ne">IndexError</span><span class="p">:</span>
<span class="c"># A "required" argument was missing. This can only happen if</span>
<span class="c"># the decorator of the function was incorrectly specified.</span>
<span class="c"># So this probably is not a user error, but a developer error.</span>
<span class="n">msg</span> <span class="o">=</span> <span class="s">"path_arg of open_file decorator is incorrect"</span>
<span class="k">raise</span> <span class="n">nx</span><span class="o">.</span><span class="n">NetworkXError</span><span class="p">(</span><span class="n">msg</span><span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">is_kwarg</span> <span class="o">=</span> <span class="bp">False</span>
<span class="c"># Now we have the path_arg. There are two types of input to consider:</span>
<span class="c"># 1) string representing a path that should be opened</span>
<span class="c"># 2) an already opened file object</span>
<span class="k">if</span> <span class="n">is_string_like</span><span class="p">(</span><span class="n">path</span><span class="p">):</span>
<span class="n">ext</span> <span class="o">=</span> <span class="n">splitext</span><span class="p">(</span><span class="n">path</span><span class="p">)[</span><span class="mi">1</span><span class="p">]</span>
<span class="n">fobj</span> <span class="o">=</span> <span class="n">_dispatch_dict</span><span class="p">[</span><span class="n">ext</span><span class="p">](</span><span class="n">path</span><span class="p">,</span> <span class="n">mode</span><span class="o">=</span><span class="n">mode</span><span class="p">)</span>
<span class="n">close_fobj</span> <span class="o">=</span> <span class="bp">True</span>
<span class="k">elif</span> <span class="nb">hasattr</span><span class="p">(</span><span class="n">path</span><span class="p">,</span> <span class="s">'read'</span><span class="p">):</span>
<span class="c"># path is already a file-like object</span>
<span class="n">fobj</span> <span class="o">=</span> <span class="n">path</span>
<span class="n">close_fobj</span> <span class="o">=</span> <span class="bp">False</span>
<span class="k">else</span><span class="p">:</span>
<span class="c"># could be None, in which case the algorithm will deal with it</span>
<span class="n">fobj</span> <span class="o">=</span> <span class="n">path</span>
<span class="n">close_fobj</span> <span class="o">=</span> <span class="bp">False</span>
<span class="c"># Insert file object into args or kwargs.</span>
<span class="k">if</span> <span class="n">is_kwarg</span><span class="p">:</span>
<span class="n">new_args</span> <span class="o">=</span> <span class="n">args</span>
<span class="n">kwargs</span><span class="p">[</span><span class="n">path_arg</span><span class="p">]</span> <span class="o">=</span> <span class="n">fobj</span>
<span class="k">else</span><span class="p">:</span>
<span class="c"># args is a tuple, so we must convert to list before modifying it.</span>
<span class="n">new_args</span> <span class="o">=</span> <span class="nb">list</span><span class="p">(</span><span class="n">args</span><span class="p">)</span>
<span class="n">new_args</span><span class="p">[</span><span class="n">path_arg</span><span class="p">]</span> <span class="o">=</span> <span class="n">fobj</span>
<span class="c"># Finally, we call the original function, making sure to close the fobj.</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">result</span> <span class="o">=</span> <span class="n">func</span><span class="p">(</span><span class="o">*</span><span class="n">new_args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">)</span>
<span class="k">finally</span><span class="p">:</span>
<span class="k">if</span> <span class="n">close_fobj</span><span class="p">:</span>
<span class="n">fobj</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
<span class="k">return</span> <span class="n">result</span>
<span class="k">return</span> <span class="n">_open_file</span></div>
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