Check whether a condition is True for any element of a list (OR operation)

Question

The list comprehension [j-x[i]==0 for i,j in enumerate(x[1:])] will produce a list of boolean elements. The return value must be a boolean scalar rather than a list. It is obtained by OR-ing all elements. How to do so?

def has_same_adjecent(x):
    if len(x)<2:
        return False
    return [j-x[i]==0 for i,j in enumerate(x[1:])]

has_same_adjecent([3,1,3,3])# must return True

score 1 · Accepted Answer · answered Jun 22 '19 at 04:17

You can do that with any (which short circuits). As an additional optimization, you can zip your list with itself shifted by 1, then compare.

def has_same_adjecent(data):
     return any(x == y for x, y in zip(data, data[1:]))

has_same_adjecent([3, 1, 3, 3])
# True

Austin · Answer 2 · 2019-06-22T04:25:29.667

1

You can also use numpy's any as well:

np.any(~np.diff(a).astype(bool))

In code:

import numpy as np

a = [3,1,3,3]
print(np.any(~np.diff(a).astype(bool)))

# True

edited Jun 22 '19 at 04:25

answered Jun 22 '19 at 04:24

Austin

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Numpy is a wonderful module, but a bit of an overkill for a simple operation like this. – cs95 Jun 22 '19 at 04:25
@cs95, fairly agree. A note to OP: this works for lists with numerical values only. – Austin Jun 22 '19 at 04:34

Check whether a condition is True for any element of a list (OR operation)

2 Answers2