How to get the closure environment in Python?

[Steven D'Aprano]

On Fri, 29 Apr 2016 02:23 am, Jin Li wrote:

> I want to get the closure environment in Python. As in the following
> example:
> 
> def func1():
>         x = 10
>         def func2():
>                 return 0
>         return func2
> 
> f=func1()
> print f()
> 
> 
> How could I get the variable `x` in the environment of `func2()`? i.e.
> `f()`.


In this case, you can't, because f is not a closure. The inner function has
to actually use a variable from the enclosing scope to be a closure -- it's
just a regular function that simply returns 0. The enclosing x does
nothing.

You can see this by inspecting f.__closure__, which is None.

If we use a better example:

def outer():
    x = 10
    def inner():
        return x + 1
    return inner

f = outer()

then you can inspect

f.__closure__[0].cell_contents

which will return 10 (the value of x).



-- 
Steven