[Python-Dev] Rationale for NamedTemporaryFile? (original) (raw)

Aaron Bingham bingham at cenix-bioscience.com
Wed Mar 21 18:25:15 CET 2007

Georg Brandl wrote:

Aaron Bingham schrieb:

Georg Brandl wrote:

Greg Ewing schrieb:

Scott Dial wrote: A tangential question -- why are TemporaryFile and NamedTemporaryFile named in TitleCase, when they're functions and not classes?

Probably because they are factory functions potentially returning a TemporaryFileWrapper. If they were "functions", they'd have to be verbed, e.g. "maketemporaryfile()". The class/function distinction is not so clear in Python from the user's point of view since there is no different calling syntax. Actually the distinction is very clear: >>> class PrivateClass(object): ... pass ... >>> def FunctionNamedToLookLikeClass(): ... return PrivateClass() ... >>> pc = PrivateClass() >>> isinstance(pc, PrivateClass) True >>> fntllc = FunctionNamedToLookLikeClass() >>> isinstance(fntllc, FunctionNamedToLookLikeClass) Traceback (most recent call last): File "", line 1, in TypeError: isinstance() arg 2 must be a class, type, or tuple of classes and types That's sure to be an unpleasant surprise for someone. duck typing... But you have a valid point. Sure, isinstance was only meant as an example. Anything that expects FunctionNamedToLookLikeClass to exhibit class-like behaviors beyond a call returning a new instance will fail.

-- Aaron Bingham Senior Software Engineer bingham at cenix-bioscience.com Tel. +49 (0)351 4173-146 Fax +49 (0)351 4173-109

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