Return bool value in pythonic way comparing within list?

Question

I am comparing fist element of list vs all the elements of list. If False is there I need to return false or if all are true, I need to return True. Currently I am doing this with if-else. is there any pythonic way to return bool value

def checker(inp):
    _compare = [ _==inp[0] for _ in inp] 
    return False if False in _compare else True

lst = [5, 5, 5]
lst2 = [5, 5, 6]

# Case 1
level = checker(inp=lst)
print(level)
True

# Case 2 
level2 = checker(inp=lst2)
print(level2)
False

Any pythonic way to achieve this

return False if False in _compare else True

Try to state your problem in a more simple manner: you want to figure out whether all items in the list are the same, whether the list is homogeneous? — deceze, Nov 29 '17 at 13:09
Yes @deceze if all the numbers in list are same I want to return True if not False — Tarun K, Nov 29 '17 at 13:10

Jean-François Fabre · Answer 1 · 2017-11-29T13:22:39.357

2

False in _compare is already a boolean so

return False not in _compare

is the best way to do it.

but looking wider:

_==inp[0] for _ in inp

should be

return all(x==inp[0] for x in inp)

so it returns False if one value is False

This solution works even if the items aren't hashable.

edited Nov 29 '17 at 13:22

answered Nov 29 '17 at 13:08

Jean-François Fabre

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`return False in _compare` gives me opposite of bool value. Case 1 returns False and Case 2 returns True – Tarun K Nov 29 '17 at 13:09
`False not in _compare` then… – deceze Nov 29 '17 at 13:13
yup thanks i wasn't sure that double negation didn't do anything. – Jean-François Fabre Nov 29 '17 at 13:18

score 1 · Accepted Answer · answered Nov 29 '17 at 13:11

1

if all the numbers in list are same I want to return True if not False

The most straight forward way:

return len(set(inp)) == 1

This does require the values to be hashable, but simple numbers are.

answered Nov 29 '17 at 13:11

deceze

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Arne · Answer 3 · 2017-11-29T13:28:01.087

1

Your problem is identical to the question "I need to check if all elements in my list are identical", since both are true for exactly the same cases. So you could also solve it like this:

def checker(inp):
    return len(set(inp)) == 1

If that is the most pythonic way to go about it .. I don't know.

edit: alternative in case of unhashable items:

def checker(inp):
    return not [True for i in range(len(inp) - 1)) if [inp[i] != inp[i+1]]

edited Nov 29 '17 at 13:28

answered Nov 29 '17 at 13:11

Arne

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You are assuming the list items are hashable. – chepner Nov 29 '17 at 13:14
@chepner washable, you could have convinced me that was a real term, it might catch on – Chris_Rands Nov 29 '17 at 13:16
1

Stupid autocorrect ;) – chepner Nov 29 '17 at 13:17
@chepner Alternative added. Comments on pythonicity? =) – Arne Nov 29 '17 at 13:28
`any(inp[i] != inp[i+1] for i in range(len(inp) - 1))` would simpler, but I'd choose https://stackoverflow.com/a/47553635/1126841 over this. – chepner Nov 29 '17 at 13:30

Return bool value in pythonic way comparing within list?

3 Answers3