Pythonic way of checking if a condition holds for any element of a list

Question

I have a list in Python, and I want to check if any elements are negative. Is there a simple function or syntax I can use to apply the "is negative" check to all the elements, and see if any of them is negative? I looked through the documentation and couldn’t find anything similar. The best I could come up with was:

if (True in [t < 0 for t in x]):
    # do something

I find this rather inelegant. Is there a better way to do this in Python?

_{Existing answers here use the built-in function any to do the iteration. See How do Python's any and all functions work? for an explanation of any and its counterpart, all.}

_{If the condition you want to check is "is found in another container", see How to check if one of the following items is in a list? and its counterpart, How to check if all of the following items are in a list?. Using any and all will work, but more efficient solutions are possible.}

Asked By: Nathan Fellman

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Source

Answer 1

any():

if any(t < 0 for t in x):
    # do something

Also, if you’re going to use “True in …”, make it a generator expression so it doesn’t take O(n) memory:

if True in (t < 0 for t in x):

Answered By: Ken

Answer 2

Use any().

if any(t < 0 for t in x):
    # do something

Answered By: Daniel Pryden

Answer 3

Python has a built in any() function for exactly this purpose.

Answered By: Amandasaurus

Answer 4

a=x.copy()
a.sort()
if a[0]<0:
    # do something

Answered By: Frost Dream

Pythonic way of checking if a condition holds for any element of a list

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