unexpected behaviour of lambda expression

[Fredrik Lundh]

leonhard.vogt at gmx.ch wrote:

> Please consider that example:
> Python 2.4.3 (#69, Mar 29 2006, 17:35:34) [MSC v.1310 32 bit (Intel)]
> on win32
> Type "help", "copyright", "credits" or "license" for more information.
>>>> s = 'foo'
>>>> f = lambda x: s
>>>> f(None)
> 'foo'
>>>> s = 'bar'
>>>> f(None)
> 'bar'
>>>> del(s)
>>>> f(None)
> Traceback (most recent call last):
>  File "<stdin>", line 1, in ?
>  File "<stdin>", line 1, in <lambda>
> NameError: global name 's' is not defined
>
> It seems to me, that f is referencing the name s instead of the string
> object bound to it

that's how lexical scoping works, of course.

if you want to bind to the object instead of the name, use explicit binding:

    f = lambda x, s=s: s

</F>