Why can't I refer to one class member in the definition of another in some cases?

Asked Dec 17 '14 at 22:07

Active Dec 17 '14 at 22:10

Viewed 24 times

I'm trying to reference one class member in the definition of another, which seems to work inside a list comprehension, but not a dict or "tuple" comprehension:

class Bork(object):
    DATA = (1, 2, 3)
    LIST = [tuple(x * x for x in DATA) for z in (4, 5, 6)]
    TUPLE = tuple(tuple(x * x for x in DATA) for z in (4, 5, 6))            # NameError: global name 'DATA' is not defined
    DICT = {z: tuple(x * x for x in DATA) for z in (4, 5, 6)}               # NameError: global name 'DATA' is not defined
    DICT2 = dict((z, tuple(x * x for x in DATA)) for z in (4, 5, 6))        # NameError: global name 'DATA' is not defined

Bork()

Am I doing something dumb, or does this seem inconsistent? This is Python 2.7 if that makes a difference.

asked Dec 17 '14 at 22:07

Doctor J

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Because generators have their own scope and list comprehension don't(only in Python 2). – Ashwini Chaudhary Dec 17 '14 at 22:12
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See e.g. http://stackoverflow.com/q/27378660/3001761 – jonrsharpe Dec 17 '14 at 22:12
See the first code snippet here: https://docs.python.org/2/reference/executionmodel.html – Ashwini Chaudhary Dec 17 '14 at 22:13

Why can't I refer to one class member in the definition of another in some cases?

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