On 04:00 pm, __pete...@web.de wrote:
Mike wrote:
I'll apologize first for this somewhat lengthy example. It does
however recreate the problem I've run into. This is stripped-down code
from a much more meaningful system.
I have two example classes, "AutoChecker" and "Snapshot" that evaluate
variables in their caller's namespace using the frame stack. As
written, the output is not what is expected: the variables evaluate to
"stagnant" values.
However, if the one indicated line is uncommented, then the result is
as expected.
So my questions are: Is this a bug in Python? Is this an invalid use
of frame data? Why does the single line "sys._getframe(1).f_locals"
fix the behavior?
A simplified demonstration of your problem:
def f(update):
... a = locals()
... x = 42
... if update: locals()
... print a
...
f(False)
{'update': False}
f(True)
{'a': {...}, 'x': 42, 'update': True}
The local namespace is not a dictionary, and the locals()/f_locals
dictionary contains a snapshot of the local namespace. Accessing the
f_locals attribute is one way to trigger an update of that snapshot.
What's puzzling is that the same dictionary is reused.
http://bugs.python.org/issue6116 is vaguely related.
Jean-Paul
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