First Python list index greater than x?

Question

What would be the most Pythonic way to find the first index in a list that is greater than x?

For example, with

list = [0.5, 0.3, 0.9, 0.8]
         


        

Answer 1

I had similar problem when my list was very long. comprehension or filter -based solutions would go thru whole list. itertools.takewhile will break the loop once condition become false first time:

from itertools import takewhile

def f(l, b): return len([x for x in takewhile(lambda x: x[1] <= b, enumerate(l))])

l = [0.5, 0.3, 0.9, 0.8]
f(l, 0.7)