Idiom gone, or did it really ever exist? () is ()
Steve Purcell
stephen_purcell at yahoo.com
Wed Apr 18 02:11:47 EDT 2001
Mike C. Fletcher wrote:
> Over the years, I've occasionally used this idiom:
>
> NULLARGUMENT = ()
>
> def someFunctionOrMethod (argument = NULLARGUMENT ):
> if argument is NULLARGUMENT:
> doSomething()
> else:
> doSomethingElse()
>
> That is, I was attempting to distinguish between a call where argument is
> passed a NULL tuple and a call where argument is passed nothing at all.
> When I was working on unit tests for my current piece of code, however, I
> discovered that this no longer works (Python 1.5.2). No idea for how long
> it hasn't worked. Now, of course, I could have used:
The convention is to use 'None' for this purpose. 'None' never changes, so
'argument is None' will work correctly for you.
-Steve
--
Steve Purcell, Pythangelist
Get testing at http://pyunit.sourceforge.net/
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