Does a two parted condition with "and"/ && stop when one part is already false?

Question

simplified example:

a = False
b = True

if a and b:
    #do stuff

Does python skip checking for b if a is already recognized as false because only one condition needs to be False for the whole statement to be False?

In my case i want to check an array for 3 conditions but want to stop if at least one of them is false (for a better runtime). Can i do

if a and b and c:
    #do stuff

or do i have to go the long way with

if a:
    if b:
        if c:
            return True
        else:
            return False
     else:
         return False
 else: 
     return False

or is there another way to check stuff like this?

It is just like how the truth table for your conditions would work. — pissall, Nov 30 '17 at 12:48
Yes. See more examples [here](https://stackoverflow.com/a/36551857/4014959) — PM 2Ring, Nov 30 '17 at 12:53
On a related note, the `all` and `any` functions also short-circuit. — PM 2Ring, Nov 30 '17 at 12:56
Or [here](https://stackoverflow.com/questions/36117583/pythonic-way-to-avoid-if-x-return-x-statements). — timgeb, Nov 30 '17 at 12:57

score 2 · Accepted Answer · answered Nov 30 '17 at 12:51

Yes, Python short-circuits.

Proof:

>>> int('ValueError')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: 'ValueError'
>>> 
>>> False and int('ValueError')
False
>>> True or int('ValueError')
True

score 2 · Answer 2 · answered Nov 30 '17 at 12:51

2

Yes, what you described above is called short circuiting and python does do that.

Similar is the case with or operation.

a or b

is short circuited at a if a is True otherwise b is checked.

answered Nov 30 '17 at 12:51

penguin2048

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Does a two parted condition with "and"/ && stop when one part is already false?

2 Answers2