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From: Peter Otten <__peter__@web.de>
Subject: Re: Set a flag on the function or a global?
Date: Tue, 16 Jun 2015 15:59:32 +0200
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Steven D'Aprano wrote:

> I have a function in a module which is intended to be used by importing
> that name alone, then used interactively:
> 
>     from module import edir
>     edir(args)
> 
> 
> edir is an enhanced version of dir, and one of the enhancements is that
> you can filter out dunder methods. I have reason to believe that people
> are split on their opinion on whether dunder methods should be shown by
> default or not: some people want to see them, others do not. Since edir
> is meant to be used interactively, I want to give people a setting to
> control whether they get dunders by default or not.
> 
> I have two ideas for this, a module-level global, or a flag set on the
> function object itself. Remember that the usual way of using this will be
> "from module import edir", there are two obvious ways to set the global:
> 
> import module
> module.dunders = False
> 
> # -or-
> 
> edir.__globals__['dunders'] = False
> 
> 
> Alternatively, I can use a flag set on the function object itself:
> 
> edir.dunders = False
> 
> 
> Naturally you can always override the default by explicitly specifying a
> keyword argument edir(obj, dunders=flag).
> 
> Thoughts and feedback? Please vote: a module global, or a flag on the
> object? Please give reasons, and remember that the function is intended
> for interactive use.

"""
In general I'm wary of routines that take flags (such as 'swapped')
that really mean "use a different version of the function" -- these
flags are almost always passed from constants and so it would be more
efficient to have a second name for the variant function.
"""
http://legacy.python.org/search/hypermail/python-1994q2/0852.html