N. Pourcelot wrote:
> I can't understand some specific behaviour of the exec statment.
>
> For example, say that I create such a class A :
>
> class A:
> def __init__(self):
> self.n = 3
> self.m = None
> def h(self, ini):
> n = self.n
> m = self.m
> if ini: exec("def m(x): return n+x"); self.m=m
> else: m(7)
>
> Now :
> obj = A()
> obj.h(1)
> obj.h(0)
>
> I get :
>
> Traceback (most recent call last):
> File "<input>", line 1, in ?
> File "<input>", line 9, in h
> File "<string>", line 1, in m
> NameError: global name 'n' is not defined
exec only supports local and global scopes; the "n" inside the exec statement
is a not a local, so it's assumed to be a global variable.
(Python's lexical scoping requires the compiler to look for free variables in
inner
scopes before generating code for the outer scope; it cannot do that for exec,
for
obvious reasons).
</F>
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