python “if len(A) is not 0” vs “if A” statements

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Category:Languages

My colleague uses this way in conditions

if len(A) is not 0:     print('A is not empty') 

I prefer this one

if A:     print('A is not empty') 

What is prop-cons arguments?

Her point is that first way is more straight-forward way to show what she exactly wants. My point is that my way is shorter.

Also first way is 2 times faster then my one:

>>> import timeit >>> timeit.timeit('len(A) is not 0', setup='A=[1,2,3]') 0.048459101999924314 >>> timeit.timeit('bool(A)', setup='A=[1,2,3]') 0.09833707799998592 

But

>>> import timeit >>> timeit.timeit('if len(A) is not 0:/n  pass', setup='A=[1,2,3]') 0.06600062699999398 >>> timeit.timeit('if A:/n  pass', setup='A=[1,2,3]') 0.011816206999810674  

second way 6 times faster! I am confused how if works :-)

 


PEP 8 style guide is clear about it:

For sequences, (strings, lists, tuples), use the fact that empty sequences are false.

Yes: if not seq:      if seq:  No:  if len(seq):      if not len(seq): 

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