Why empty string in a non empty dictionary is true in python? [duplicate]

Question

I do not understand the logical idea of this behavior:

d = {'a': 'a',
     'b': 'b',
     }

print('' in d['a']) #---> True
print(d['a'] in '') #---> False

can someone help me?

This has nothing to do with the dictionary, In Python the empty string is inside any non-empty string — DeepSpace
– DeepSpace, Commented Apr 22, 2021 at 20:35
@wjandrea I think that's what was confusing the OP. A common confusion thinking it would return false because '' is not in d. (I'm just speculating) — LPR
– LPR, Commented Apr 22, 2021 at 20:36
Did you mean to use ==? in is almost never commutative. The only exception is when == is True. — Mad Physicist
– Mad Physicist, Commented Apr 22, 2021 at 20:36

LPR · Accepted Answer · 2021-04-22 20:40:26Z

2

It's because it's searching the string 'a', if you ask if an empty string is in a non-empty string (or an empty string) it will return true.

What you are really asking is:

'' in 'a'

Out: True  # Notice that 'a' is the same as '' + 'a'

'a' in ''

Out: False

answered Apr 22, 2021 at 20:34

LPR

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