When I evaluate the following expression:
1 or (1/0) and 1
What are the rules (precedence, short-circuit evaluation etc) are followed to get the answer
Asked
Active
Viewed 714 times
2
Craig Burgler
- 1,749
- 10
- 19
Omar Khan
- 412
- 2
- 12
-
This question has NOT been already asked. The question that refers to the priority of NOT AND & OR in python does not address the short circuit evaluation taking place here. – Omar Khan Sep 07 '16 at 14:48
2 Answers
2
b or anything_else is defined to return b if b is true-ish, without evaluating anything_else. Since your first 1 is true-ish, your 1/0 never gets evaluated, hence no error. By "true-ish" I mean any value that Python considers true, not only the True boolean value. Try your expression with True or [2] in place of the first 1 to see what I mean.
D-Von
- 416
- 2
- 5
-
Can post the link to the official documentation containing this information? – Omar Khan Sep 07 '16 at 14:53
-
For Python 2: https://docs.python.org/2/reference/expressions.html#boolean-operations – D-Von Sep 07 '16 at 15:19
1
Python short-circuit evaluates. In your example, the expression
1 or (1/0) and 1
finishes evaluation at the first 1 and returns True.
A more minimal example serves to illustrate Python's short-circuit evaluation. Consider the expression:
(1/0) or 1
This raises a ZeroDivisionError exception upon evaluation of (1/0). But the expression:
1 or (1/0)
short-circuit evaluates to True. No exception is raised since the sub-expression (1/0) never gets evaluated.
Craig Burgler
- 1,749
- 10
- 19