This documents an unmaintained version of NetworkX. Please upgrade to a maintained version and see the current NetworkX documentation.

Source code for networkx.utils.decorators

import sys

from collections import defaultdict
from os.path import splitext

import networkx as nx
from decorator import decorator
from networkx.utils import is_string_like

__all__ = [

def not_implemented_for(*graph_types):
    """Decorator to mark algorithms as not implemented

    graph_types : container of strings
        Entries must be one of 'directed','undirected', 'multigraph', 'graph'.

    _require : function
        The decorated function.

    If any of the packages cannot be imported

    Multiple types are joined logically with "and".
    For "or" use multiple @not_implemented_for() lines.

    Decorate functions like this::

       def sp_function():

       def sp_np_function():
    def _not_implemented_for(f,*args,**kwargs):
        graph = args[0]
        terms= {'directed':graph.is_directed(),
                'undirected':not graph.is_directed(),
                'graph':not graph.is_multigraph()}
        match = True
            for t in graph_types:
                match = match and terms[t]
        except KeyError:
            raise KeyError('use one or more of ',
                           'directed, undirected, multigraph, graph')
        if match:
            raise nx.NetworkXNotImplemented('not implemented for %s type'%
                                            ' '.join(graph_types))
            return f(*args,**kwargs)
    return _not_implemented_for

def _open_gz(path, mode):
    import gzip
    return gzip.open(path,mode=mode)

def _open_bz2(path, mode):
    import bz2
    return bz2.BZ2File(path,mode=mode)

# To handle new extensions, define a function accepting a `path` and `mode`.
# Then add the extension to _dispatch_dict.
_dispatch_dict = defaultdict(lambda : open)
_dispatch_dict['.gz'] = _open_gz
_dispatch_dict['.bz2'] = _open_bz2
_dispatch_dict['.gzip'] = _open_gz

[docs]def open_file(path_arg, mode='r'): """Decorator to ensure clean opening and closing of files. Parameters ---------- path_arg : int Location of the path argument in args. Even if the argument is a named positional argument (with a default value), you must specify its index as a positional argument. mode : str String for opening mode. Returns ------- _open_file : function Function which cleanly executes the io. Examples -------- Decorate functions like this:: @open_file(0,'r') def read_function(pathname): pass @open_file(1,'w') def write_function(G,pathname): pass @open_file(1,'w') def write_function(G, pathname='graph.dot') pass @open_file('path', 'w+') def another_function(arg, **kwargs): path = kwargs['path'] pass """ # Note that this decorator solves the problem when a path argument is # specified as a string, but it does not handle the situation when the # function wants to accept a default of None (and then handle it). # Here is an example: # # @open_file('path') # def some_function(arg1, arg2, path=None): # if path is None: # fobj = tempfile.NamedTemporaryFile(delete=False) # close_fobj = True # else: # # `path` could have been a string or file object or something # # similar. In any event, the decorator has given us a file object # # and it will close it for us, if it should. # fobj = path # close_fobj = False # # try: # fobj.write('blah') # finally: # if close_fobj: # fobj.close() # # Normally, we'd want to use "with" to ensure that fobj gets closed. # However, recall that the decorator will make `path` a file object for # us, and using "with" would undesirably close that file object. Instead, # you use a try block, as shown above. When we exit the function, fobj will # be closed, if it should be, by the decorator. @decorator def _open_file(func, *args, **kwargs): # Note that since we have used @decorator, *args, and **kwargs have # already been resolved to match the function signature of func. This # means default values have been propagated. For example, the function # func(x, y, a=1, b=2, **kwargs) if called as func(0,1,b=5,c=10) would # have args=(0,1,1,5) and kwargs={'c':10}. # First we parse the arguments of the decorator. The path_arg could # be an positional argument or a keyword argument. Even if it is try: # path_arg is a required positional argument # This works precisely because we are using @decorator path = args[path_arg] except TypeError: # path_arg is a keyword argument. It is "required" in the sense # that it must exist, according to the decorator specification, # It can exist in `kwargs` by a developer specified default value # or it could have been explicitly set by the user. try: path = kwargs[path_arg] except KeyError: # Could not find the keyword. Thus, no default was specified # in the function signature and the user did not provide it. msg = 'Missing required keyword argument: {0}' raise nx.NetworkXError(msg.format(path_arg)) else: is_kwarg = True except IndexError: # A "required" argument was missing. This can only happen if # the decorator of the function was incorrectly specified. # So this probably is not a user error, but a developer error. msg = "path_arg of open_file decorator is incorrect" raise nx.NetworkXError(msg) else: is_kwarg = False # Now we have the path_arg. There are two types of input to consider: # 1) string representing a path that should be opened # 2) an already opened file object if is_string_like(path): ext = splitext(path)[1] fobj = _dispatch_dict[ext](path, mode=mode) close_fobj = True elif hasattr(path, 'read'): # path is already a file-like object fobj = path close_fobj = False else: # could be None, in which case the algorithm will deal with it fobj = path close_fobj = False # Insert file object into args or kwargs. if is_kwarg: new_args = args kwargs[path_arg] = fobj else: # args is a tuple, so we must convert to list before modifying it. new_args = list(args) new_args[path_arg] = fobj # Finally, we call the original function, making sure to close the fobj. try: result = func(*new_args, **kwargs) finally: if close_fobj: fobj.close() return result return _open_file