python "if len(A) is not 0" vs "if A" statements

Question

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 :-)

Answer 1

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):

Answer 2

I would argue that if A = 42, your colleague code would raise an error

object of type 'int' has no len()

while your code would just execute whatever comes after the if.