Ethan Furman wrote:
Ethan Furman wrote:
Ian Kelly wrote:
I am not a dev, but I believe it works because assigning to locals()
and assigning via exec are not the same thing. The problem with
assigning to locals() is that you're fundamentally just setting a
value in a dictionary, and even though it happens to be the locals
dict for the stack frame, Python can't figure out that it should go
and update the value of the optimized local to match. exec, on the
other hand, compiles and executes an actual STORE_NAME operation. Of
course, if the particular local variable hasn't been optimized by the
compiler, then updating locals() works just fine (although you
probably should not rely on this):
def f(x, y):
... locals()[x] = y
... print locals()[x]
... exec 'print ' + x
...
f('a', 42)
42
42
Definitely should rely on it, because in CPython 3 exec does not
un-optimize the function and assigning to locals() will not actually
change the functions variables.
Ouch, that should have been *not* rely on it; not because it doesn't
work (exec uses locals() if one is not specified), but because it is
easy for the names in the function to get out of sync with the names in
the functions locals() (or __dict__).
I should stop answering now :( Ignore the __dict__ comment, it is
incorrect.
~Ethan~
--
http://mail.python.org/mailman/listinfo/python-list
