Hello,
How would you feel if explicit parens were used to convey additional
semantic meaning? That seems like a pretty dumb question, because,
well, parens *are* used to convey additional semantic meaning. E.g.:
1 + 2 + 3 vs 1 + (2 + 3)
The result is the same, but somehow I wanted to emphasize that 2 and 3
should be added together, and somehow else.
a + b + c vs a + (b + c)
Here, there's even no guarantee of the same result, if we have user
objects with weirdly overloaded __add__().
Thanks for hanging with me so far, we're getting to the crux of the
question:
Do you think there can be difference between the following two
expressions:
obj.meth()
(obj.meth)()
?
The question is definitely with a trick (why else there would be the
intro), and first answer which comes to mind might not be the right
one. As a hint, to try to get a grounded answer to that question, it
would be useful to look at the difference in disassembly of the above
code in CPython3.6 vs CPython3.7 (or later):
python3.6 -m dis meth_call.py
python3.7 -m dis meth_call.py
Then, to try to explain the difference at the suitable level of
abstraction. If that doesn't provide enough differentiation, it might
be helpful to add the 3rd line:
t = obj.meth; t()
And run all 3 lines thru CPython3.7, and see if the pattern is now
visible, and a distortion in the pattern too.
What would be the explanation for all that?
For reference, the disassembly of the 3 lines with CPython3.7 is
provided:
1 0 LOAD_NAME 0 (obj)
2 LOAD_METHOD 1 (meth)
4 CALL_METHOD 0
6 POP_TOP
2 8 LOAD_NAME 0 (obj)
10 LOAD_METHOD 1 (meth)
12 CALL_METHOD 0
14 POP_TOP
3 16 LOAD_NAME 0 (obj)
18 LOAD_ATTR 1 (meth)
20 STORE_NAME 2 (t)
22 LOAD_NAME 2 (t)
24 CALL_FUNCTION 0
26 POP_TOP
...
--
Best regards,
Paul mailto:[email protected]
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