On 15 Sep 2006 00:18:14 -0700, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > Hi everyone, > > Maybe these questions will sound strange to you, but I sometime have a > hard time switching from Java to Python ;-) > > Let's say I have a function like this : > > def show_lines(file): > for next_line in file: > ... > > What can I do to be sure that the input argument is indeed a 'File' > object ? > > #1 : should I start by checking that 'file' is indeed an instance of a > File object ? (and how do I do this ?) > #2 : should I do nothing ? (but I don't like the idea of risking to > have a runtime exception raised somewhere) > > Thanks for helping... > > -- > http://mail.python.org/mailman/listinfo/python-list >
Do nothing! The caller might pass you a file-like object, and you can never be exactly sure. Duck typing rules in this case. If what they pass acts like a file, then it must be a file (for as much as the function needs to care, anyway). Don't want to risk an exception at runtime? Well, isn't that what you would do if you explicitly checked for a file object and had something else, anyway? Just assume its a file and if there is an error it should propogate because one of the callers messed up and should know that. -- http://mail.python.org/mailman/listinfo/python-list
