[EMAIL PROTECTED] wrote:
> I just came across http://www.perl.com/pub/a/2002/05/29/closure.html
> and wanted to try the "canonical example of closures" in Python. I
> came up with the following, but it fails:
>
> #######################
> #!/usr/bin/env python
>
> def make_counter(start_num):
> start = start_num
> def counter():
> start += 1
> return counter
The other answers you got will work, but here's an alternative to
consider: you can convert the function into a generator and then just
move the variable inside.
>>> def make_counter(start_num):
def counter():
start = start_num
while 1:
yield start
start += 1
return counter().next
>>> from_ten = make_counter(10)
>>> from_three = make_counter(3)
>>> print from_ten()
10
>>> print from_ten()
11
>>> print from_three()
3
>>> print from_ten()
12
>>> print from_three()
4
>>>
While I realise you are just trying a simple example, if you actually
wanted the code the truly Pythonic way would be to use the existing
libraries:
>>> import itertools
>>> def make_counter(start_num):
return itertools.count(start_num).next
>>> from_ten = make_counter(10)
>>> from_three = make_counter(3)
>>> print from_ten()
10
>>> print from_ten()
11
>>> print from_three()
3
>>> print from_ten()
12
>>> print from_three()
4
>>>
Never reinvent the wheel unless you really need a square one. :^)
--
Duncan Booth http://kupuguy.blogspot.com
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