improvement for compiler-generated python for 'None' object comparisons
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Key: THRIFT-1107
URL: https://issues.apache.org/jira/browse/THRIFT-1107
Project: Thrift
Issue Type: Improvement
Components: Python - Compiler
Reporter: Will Pierce
Assignee: Will Pierce
The python code generator produces several python statements, especially the
{{write()}} methods' per-field code, that compares something to None using
'{{!= None}}', when it is more efficient to use the '{{is not None}}'
expression.
>From what I understand, in python it's almost always true that ({{x \!=
>None}}) == ({{x is not None}}), but the actual implementation and intent is
>very different. The '{{\!= None}}' comparison does a by-value comparison that
>does much more work than an object identity '{{is not None}}' comparison does.
The actual performance impact isn't much, but I benchmarked the performance of
'{{x is not None}}' to '{{x \!= None}}' and got some interesting results. In
python 2.4, 2.7 and 3.1, it's about 2-3 times as fast to use '{{is not None}}'
over '{{\!= None}}'.
I'll attach a patch to switch to 'is not None', and attach a simple benchmark
test script exercising '{{is not None}}' vs. '{{\!= None}}' and post the
performance measurements to this ticket.
These URLs are somewhat relevant about this specific issue in general:
* http://www.python.org/dev/peps/pep-0008/ (Search for 'singletons', or scroll
to 'Programming Recommendations' item 2)
*
http://stackoverflow.com/questions/100732/why-is-if-not-someobj-better-than-if-someobj-none-in-python
- Stack Overflow question about the same, though it veers into the cost of
typecasting to bool, which isn't relevant here
* http://jaredgrubb.blogspot.com/2009/04/python-is-none-vs-none.html - a
similar experience and test results that match
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