python_class_closure

>>> class Works(object):
...     a = 1
...     b = [a + x for x in range(10)]
>>> Works.a
0: 1
>>> Works.b
1: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> class DoesntWork(object):
...     a = 1
...     b = (a + x for x in range(10))
>>> DoesntWork.a
2: 1
>>> DoesntWork.b
3: <generator object <genexpr> at 0x00000000029E2B40>
>>> for i in DoesntWork.b:
...     print i
Traceback (most recent call last):
  File "<pyshell#6>", line 1, in <module>
    for i in DoesntWork.b:
  File "<pyshell#3>", line 3, in <genexpr>
    b = (a + x for x in range(10))
NameError: global name 'a' is not defined
>>> def foo():
...     a = 1
...     return list(a + x for x in xrange(10))
>>> foo()
4: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> class DoesntWork2(object):
...     a = 1
...     b = list(a + x for x in range(10))
Traceback (most recent call last):
  File "<pyshell#9>", line 1, in <module>
    class DoesntWork2(object):
  File "<pyshell#9>", line 3, in DoesntWork2
    b = list(a + x for x in range(10))
  File "<pyshell#9>", line 3, in <genexpr>
    b = list(a + x for x in range(10))
NameError: global name 'a' is not defined