I if not x is none thought a good representation to read more.
google style guide in if x is not none , to write.
Is it because of the speed difference between you two?
Or is it because if not x is None is less readable?
The reason why if xis not None is recommended instead of not xisy when writing code is because
In the compiler, no matter what you use, you use not (xisy) in the same way
This is because there is room for human reading to be interpreted as (not x) is y.
As shown below, there is no difference in performance speed because the two are compiled in the same byte code.
Python 2.6.2
>>> import dis
>>> def f(x):
... ... return x is not None
...
>>> dis.dis(f)
2 0 LOAD_FAST 0 (x)
3 LOAD_CONST 0 (None)
6 COMPARE_OP 9 (is not)
9 RETURN_VALUE
>>> def g(x):
... ... return not x is None
...
>>> dis.dis(g)
2 0 LOAD_FAST 0 (x)
3 LOAD_CONST 0 (None)
6 COMPARE_OP 9 (is not)
9 RETURN_VALUE
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