[Python-Dev] file(file)

Sat Jan 13 14:25:09 CET 2007

 Terry Reedy schrieb:
> | > We should also consider the semantics in more detail. Should the seek
> | > position be shared between the two objects? What about buffering?
> |
> | That's definitely the hard part. But it's somewhat similar to
> | "normal" mutable objects which are (I think always, right?) shallow
> | copied when used in a constructor.
>> But why, in the normal case, do you want a copy? It seems to me that is 
> thefile is a file rather than a string, then that is what you want, and you 
> are asking for
> 'thefile = file(thefile)' to work just as the iter statement does.

Consider the use case presented before:
def foo(thefile):
 if type(thefile) == str:
 thefile = open(thefile)
Now, if thefile is already a file object, you won't have to close it
because it came from somewhere else. If thefile is a string, you'll have to
close it at the end.
Now, if file(fileobject) would return another file object created by
something like os.dup(), you can do
def foo(thefile):
 try:
 thefile = file(thefile)
 (...)
 finally:
 thefile.close()
Georg