Andrea Griffini wrote:
> [EMAIL PROTECTED] wrote:
>
>> The following code:
>>
>> def functions():
>> l=list()
>> for i in range(5):
>> def inner():
>> return i
>> l.append(inner)
>> return l
>>
>>
>> print [f() for f in functions()]
>>
>>
>> returns [4,4,4,4,4], rather than the hoped for [0,1,2,3,4]. I presume
>> this is something to do with the variable i getting re-bound every time
>> we go through the loop, or something, but I'm not sure how to fix this.
>
>
> The problem is that "i" inside the function is indeed
> the same variable for all the functions (the one you're
> using for looping).
>
> If you want a different variable for each function
> you can use the somewhat ugly but idiomatic
>
> def functions():
> l=list()
> for i in range(5):
> def inner(i=i):
> return i
> l.append(inner)
> return l
>
> this way every function will have its own "i" variable,
> that is initialized with the value of the loop variable
> when executing the "def" statement.
>
> Andrea
Yet another way to skin the same cat, maybe even less ugly, depending on taste.
def make_inner(i):
def inner():
return i
return inner
def functions():
return [make_inner(i) for i in range(5)]
print [f() for f in functions()]
James
--
James Stroud
UCLA-DOE Institute for Genomics and Proteomics
Box 951570
Los Angeles, CA 90095
http://www.jamesstroud.com/
--
http://mail.python.org/mailman/listinfo/python-list
