tkFileDialog question

[Gabriel Genellina]

En Fri, 13 Nov 2009 11:32:37 -0300, Matt Mitchell  
<mmitchell at transparent.com> escribió:

> answer = tkFileDialog.askdirectory()
>
> if answer is not '':
> 	#do stuff

Although it "reads well", this is *wrong*. You want != here, not the `is  
not` operator.

if answer != '': ...

If you want to compare the *values* of two objects, to see if they are  
equal or not, use == or !=.
If you want to compare *identity*, to see if two results refer to the very  
same object or not, use `is` or `is not`

(In your example, it *may* appear to work, because CPython optimizes very  
short strings like 'a' or '', but you should not rely on this optimization)

-- 
Gabriel Genellina