CODEWITHSUNDEEP
pythonoperator-precedence
Manu
Manu

Reputation: 113

and operation in python

Following is the code that is yielding confusing results.

a = None
b = 1
print a and b
if a and b is None:
    print "True"
else:
    print "False"

Here bool(a) is false as it's none. So via short circuit, the expression should return None. This is actually happening. However, during if condition, the condition fails. Although a and b yields None, the condition fails and priting false at the output. Can someone explain why it's happening?

Upvotes: 1

Views: 59

Answers (1)

Jack Taylor
Jack Taylor

Reputation: 6237

a and b is None is evaluated the same as a and (b is None), so the expression evaluates to None, and execution jumps to the else clause.

If you add brackets (a and b) is None, then your code will print "True" as you expect.

This is because is has a higher precedence than and in Python. Take a look at the operator precedence documentation for more details.

Upvotes: 7

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