Logic rules of Python's `if` clause

Question

I have an if condition in my code which seems for example like this:

a = [1,2,3]
b = [4,5,6]
c = [7,8,9]

I want 'If' to return true when (1 is in a) or (1 is in b) or (1 is in c) or (5 is in a) or (5 is in b) or (5 is in c)

I've tried:

if (1 or 5) in (a or b or c):
    pass

But this obviously didn't work that way. Could you give me a hint? Thanks

`(1 or 5)` is evaluated to 1, since it's True and `int(True)` is 1. — Maroun, Oct 07 '14 at 14:23
And `(a or b or c)` evaluates to `a` since that is non-empty. Together you essentially have `1 in a`. — Martijn Pieters, Oct 07 '14 at 14:24
try `if 1 in a or 4 in b:` something like this. you can get better better for this. so just explore a little. — Vishnu Upadhyay, Oct 07 '14 at 14:34
You almost had it: `if (1 in a) or (1 in b) or (1 in c) or (5 in a) or (5 in b) or (5 in c):` — Mark Ransom, Oct 07 '14 at 15:27

score 2 · Answer 1 · answered Oct 07 '14 at 14:25

You should probably use sets:

a = {1, 2, 3}
b = {4, 5, 6}
c = {7, 8, 9}

a | b | c
#>>> {1, 2, 3, 4, 5, 6, 7, 8, 9}

{1, 5} & (a | b | c)
#>>> {1, 5}

bool({1, 5} & (a | b | c))
#>>> True

if {1, 5} & (a | b | c):
    print("Yeah!")
#>>> Yeah!

if not {1, 5}.isdisjoint(a | b | c):
    print("Yeah!")    
#>>> Yeah!

If you want short-circuiting:

if not all({1, 5}.isdisjoint(items) for items in (a, b, c)):
    print("Yeah!")    
#>>> Yeah!

score 0 · Accepted Answer · answered Oct 07 '14 at 15:03

0

This seems to work for me, though there might be a built in to concatenate the three lists.

a = [1,2,3]
b = [4,5,6]
c = [7,8,9]  
target = [1,5]

any(x for x in (a+b+c) if x in target)

True

answered Oct 07 '14 at 15:03

marceljg

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Logic rules of Python's `if` clause

2 Answers2