Need help to understand code in python

Question

first = int(input('first int: '))
second = int (input('second int: '))
result =0
if first and second:
result =1
elif not first:
    result =2
elif first or second:
    result=3
else:
    result=4
print(result)

when I enter 1 and 0, the result is 3. I would appreciate if anyone could add some explanation.

No that's not a possible duplicate. Can't be! – Bleeding Fingers Feb 10 '14 at 06:55 — Bleeding Fingers, Feb 10 '14 at 06:55
Edited my answer to answer your latest question. – gravetii Feb 10 '14 at 07:05 — gravetii, Feb 10 '14 at 07:05

gravetii · Accepted Answer · 2014-02-10T09:23:01.533

2

You are using or- it means the statement will return True when it first finds True. When you say 5 or 9, both 5 and 9 represent truism (as does any non-zero value). So it returns the first - 5 in this case. When you say 9 or 5, it returns 9.

EDIT: k = 1 or 0 would evaluate to True since 1 represents truism. Thus, as per your code, result is 3

edited Feb 10 '14 at 09:23

answered Feb 10 '14 at 06:52

gravetii

8,485
8
49
69

"both 5 and 9 are vacuously `True`" - this is a very misleading description of what Python considers "true". – user2357112 Feb 10 '14 at 06:55
agreed...edited accordingly. – gravetii Feb 10 '14 at 06:57

atupal · Answer 2 · 2014-02-10T07:04:56.540

0

In many program languages, the boolean operations only evaluate their second argument if needed for their outcome. These called short-circuit operator. And in python, according the docs, it returns:

x or y  :   if x is false, then y, else x
x and y :   if x is false, then x, else y

edited Feb 10 '14 at 07:04

answered Feb 10 '14 at 06:59

atupal

15,266
5
29
41

Need help to understand code in python

2 Answers2