Vitja Makarov, 15.08.2011 07:49:
2011/8/15 Vitja Makarov:
When creating python-class dict it seems that CPython first looks at
dict then at globals:
A = 1
class X:
A = A
def y():
A = 3
class Y:
A = A
return Y
Y = y()
print(X.A, Y.A)
Will print: 1, 1
And not: 1, 3
I didn't find documentation for this but if I'm correct that should be
easy to fix issue in Cython.
Now for this code cython reports compile-time error: local variable
referenced before assignment
One more interesting example:
A = 1
def foo(a):
A = a
class X:
a = A
A = A
class Y:
a = A
return X, Y
X, Y = foo(666)
print X.a, X.A, Y.a
This prints "1 1 666". However, at least to me, the most surprising thing
is this:
>>> A = 1
>>> def foo(x):
... A = x
... class X:
... a = A
... return X
...
>>> foo(2).a
2
>>> def foo(x):
... A = x
... class X:
... A = A
... return X
...
>>> foo(2).A
1
That looks pretty sick, but I would guess that the 'reasoning' behind this
is that the second case contains an assignment to A inside of the class
namespace, and assignments make a variable local to a scope, in this case,
the function scope. Therefore, the A on the rhs is looked up in that scope
as well. However, this is just a hand waving guess. I just asked on c.l.py,
we may get a pointer to relevant documentation that way.
Also see this bug:
http://trac.cython.org/cython_trac/ticket/671
Stefan
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