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Re: Why lambda in loop requires default?

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gvim writes:

> Given that Python, like Ruby, is an object-oriented language why
> doesn't this:
>
> def m():
>   a = []
>   for i in range(3): a.append(lambda: i)
>   return a
>
> b = m()
> for n in range(3): print(b[n]())  # =>  2  2  2

I'm going to suggest two variations that may or may not work for you,
with very brief glosses. Just ignore them if you don't see their
relevance.

First, consider:

def w():
  a = []
  for i in range(3): a.append(lambda: i)
  i = "!"
  return a

b = w()
for f in b: print(f()) # => ! ! !

(Those functions depend on the i in the loop.)

> lambda i=i: i
>
> ... is needed to make it work in Python. Just wondered why?

And second, consider: lambda x=i: x

(Those functions are independent of the i in the loop.)

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Why lambda in loop requires default? gvim <gvimrc@gmail.com> - 2016-03-27 02:46 +0100
  Re: Why lambda in loop requires default? Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-03-27 17:16 +0300
  Re: Why lambda in loop requires default? Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-03-27 18:15 +0300
  Re: Why lambda in loop requires default? Ned Batchelder <ned@nedbatchelder.com> - 2016-03-27 08:29 -0700

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