In operator confusing example

Question

Hi,

In the following code snippet:

arr = ["a", True]
print("a" in arr in arr) #False

I feel like this should either err (trying to check if “a” is in True) or give True (True is in arr). However it gives false, how do you explain it?

Answer 1

Edward Finkelstein ,

python evaluates this expression like: (read more in python reference/ expressions)
see also this thread in stackoverflow.com:
https://stackoverflow.com/questions/60400708/why-a-in-arr-in-arr-a-in-arr-in-arr#60400956

first evaluation: ("a" in arr) => True
second evaluation: (arr in arr) => False, because arr is not in arr
True and False => False

if we use parenthesis for grouping, the result is different:
print(("a" in arr) in arr) => True

Answer 2

Here is a similar question:

https://www.sololearn.com/Discuss/2166930/?ref=app

If I understand it correct it first checks if "a" in arr (True), then it checks if arr in arr (False).

True and False leads to False.

Answer 3

EDIT: I'm wrong. Always learning! Check answers below 👍