Closure/method definition question (delete 'for Python 2.7')
tjreedy at udel.edu
Mon Mar 10 19:59:10 CET 2014
On 3/10/2014 1:27 PM, Brunick, Gerard:(Constellation) wrote:
> class Test(object):
> x = 10
> def __init__(self):
> self.y = x
> t = Test()
> NameError: global name 'x' is not defined.
> in Python 2.7.
In Python, period.
> I would assume that when __init__ is being defined,
> it is just a regular old function
Right. It is an attribute of the class much like other object. This is
more obvious and more consistent in Python 3. In Python 3, these two
code snippets have the same effect.
def f(self): return self.a
g = C.f # in2.x, C.f.im_func
def g(self): return self.a
class C: pass
C.f = g
This is possible because functions are only loosely coupled to the class
they are defined in, through the public attribute mechanism. This is
handy for testing. There is no private namespace tie. As long as self.a
exists, g could function even if the class C object were deleted or
A function that accesses module globals *does* have a private namespace
tie to the module it is defined in (lexical scoping), and this must be
accounted for when testing or otherwise using it in another module --
perhaps by altering the original module.
> and x is a variable in an outer scope,
Non-global 'outer scope' is peculiar to lexically nested functions. Any
nonlocal access ties a function to its outer function through private
Terry Jan Reedy
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