Re: [Python-ideas] contextlib.maybe

On 12/11/2011 12:07 AM, Julian Berman wrote:

Twice recently I've found myself wanting to write the following code:

 def fn(a_file=None):
     responsible_for_closing = False

     if a_file is None:
         a_file = open(a_default_location)
         responsible_for_closing = True

     do_stuff(a_file)

     if responsible_for_closing:
         a_file.close()

which can be written slightly shorter I know, but it's still a tiny bit messy and repetitive. What I'd prefer to write is something more like:

 def fn(a_file=None):
     with contextlib.maybe(a_file, open, default) as a_file:
         do_stuff(a_file)

Expecting contextlib to have such a specialized context manager that does exactly what you want is perhaps too much. However, you should be able to write a class yourself that keeps the flag and does the conditional opening and closing in the __enter__ and __exit__ methods.