[Python-Dev] 2.5 and beyond

[Nick Coghlan]

Giovanni Bajo wrote:
> Yes but:
> 
>>>> a = []
>>>> for i in range(10):
> ...     a.append(lambda: i)
> ...
>>>> print [x() for x in a]
> [9, 9, 9, 9, 9, 9, 9, 9, 9, 9]
> 
> This subtle semantic of lambda is quite confusing, and still forces people to
> use the "i=i" trick.

If you'd like each function instance to have a separate closure scope, then 
*give* each function a separate closure scope, instead of making them all 
share the same one the way you have above:

 >>> def make_f(i):
...     def f():
...         return i
...     return f
...
 >>> a = []
 >>> for i in range(10):
...     a.append(make_f(i))
...
 >>> print [x() for x in a]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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