Assert that all values are negative or all values are non-negative

Question

I need to assert that all numeric values in an array are either negative or non-negative.

I wrote this:

def check(arr):
    return all([i < 0 for i in arr]) or all([i >= 0 for i in arr])

And this, which is slightly more efficient I suppose:

def check(arr):
    temp = [i < 0 for i in arr]
    return all(temp) or not any(temp)

I would like to know if there's a cleaner / more pythonic way, or perhaps some arithmetic trick which I can use instead.

You can check any element is thesame with the rest `all(x == temp[0] for x in temp)` but using numpy would be the easiest — percusse, May 21 '18 at 12:27

jpp · Answer 1 · 2018-05-21T12:31:28.717

2

One way is to use a set comprehension to derive a set of Boolean values. This set will be either {True}, {False} or {True, False}. Then test if your set has length equal to 1.

def check(arr):
    return len({i < 0 for i in arr}) == 1

edited May 21 '18 at 12:31

answered May 21 '18 at 12:30

jpp

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Create a `dict` and making sure it doesn't contain both `true` and `false`? – goodvibration May 21 '18 at 12:31
@goodvibration, I think a `dict` may be overkill here. – jpp May 21 '18 at 12:31
1

Nice, and with a single iteration – DeepSpace May 21 '18 at 12:32

Assert that all values are negative or all values are non-negative

1 Answers1