- open_file(path_arg, mode='r')[source]#
Decorator to ensure clean opening and closing of files.
- path_argstring or int
Name or index of the argument that is a path.
String for opening mode.
Function which cleanly executes the io.
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 of how to handle this case:
@open_file("path") def some_function(arg1, arg2, path=None): if path is None: fobj = tempfile.NamedTemporaryFile(delete=False) 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 try: fobj.write("blah") finally: if path is None: fobj.close()
Normally, we’d want to use “with” to ensure that fobj gets closed. However, the decorator will make
patha file object for us, and using “with” would undesirably close that file object. Instead, we use a try block, as shown above. When we exit the function, fobj will be closed, if it should be, by the decorator.
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("pathname","w") def write_function(G, pathname="graph.dot"): pass @open_file("path", "w+") def another_function(arg, **kwargs): path = kwargs["path"] pass