Diez said:
Classes are not scopes.
So the above doesn't work because name resolution inside functions/methods
looks for local variables first, then for the *global* scope. There is no
class-scope-lookup.
But http://docs.python.org/tutorial/classes.html says, in Section 9.3 "A
First Look at Classes":
When a class definition is entered, a new namespace is created,
and used as the local scope — thus, all assignments to local variables
go into this new namespace. In particular, function definitions bind
the name of the new function here.
The following example confirms this:
class Spam(object):
clsvar_1 = 555
clsvar_2 = clsvar_1 + 222
def __init__(self):
print "Spam instance initialized"
sp = Spam()
print sp.clsvar_1, sp.clsvar_2
output:
Spam instance initialized
555 777
Does the OP (kj) have a legitimate gripe, though? I confess that I know
nothing about Python's implementation -- I'm strictly a user. So it's
just a suspicion of mine that
something special enables a recursive function definition to refer to
the function's own name before the definition has been completed. It
works at the module-namespace (i.e. global) level, and Diez's "toy
example" shows that it works at function-namespace level:
class Demo(object):
def fact(n):
def inner(n):
if n < 2:
return 1
else:
return n * inner(n - 1)
return inner(n)
_classvar = fact(5)
So why can't it work at the class-namespace level, too?
(BTW, Diez, your toy example is another demonstration that there *is* a
class-scope-lookup: the "def" statement binds the name "fact" in the
class scope, and the assignment statement looks up the name "fact" in
that scope.)
-John
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