Find index of first element with condition in numpy array in python

Question

I'm trying find the index of the first element bigger than a threshold, like this:

index = 0
while timeStamps[index] < self.stopCount and index < len(timeStamps):
    index += 1

Can this be done in a one-liner? I found:

index = next((x for x in timeStamps if x <= self.stopCount), 0)

I'm not sure what this expression does and it seems to return 0 always... Could somebody point out the error and explain the expression?

Answer 1

Another option is to use np.argmax (see this post for details). So your code would become something like

(timeStamps > self.stopCount).argmax()

the caveat is that if the condition is never satisfied the argmax will return 0.