Oddity in 2.4 with eval('None')

Fredrik Lundh fredrik at pythonware.com
Mon Dec 20 22:33:15 CET 2004


Leif K-Brooks wrote

>> Yes. "print eval('None')" is printing the value of None as defined in your module's global 
>> namespace:
>
> Right, but why? The expression "None" doesn't worry about the global namespace when used in normal 
> code; why does it when used in eval()ed code?

from what I can tell, the mapping of the None symbol to a constant is done
in the peephole optimizer, which doesn't seem to be used when compiling
expressions.

in 2.4:

>>> dis.dis(compile("None", "", "exec"))
  1           0 LOAD_CONST               0 (None)
              3 POP_TOP
                ...
>>> dis.dis(compile("None", "", "eval"))
  0           0 LOAD_NAME                0 (None)
              3 RETURN_VALUE

in 2.3:

>>> dis.dis(compile("None", "", "exec"))
  1           0 LOAD_NAME                0 (None)
              3 POP_TOP
                ...
>>> dis.dis(compile("None", "", "eval"))
  0           0 LOAD_NAME                0 (None)
              3 RETURN_VALUE

</F> 






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