bisect

Find insertion positions in an already sorted list. Searching takes logarithmic time; insertion still moves list elements and can take linear time.

Function	Result
`bisect_left(a, x, lo=0, hi=None)`	Index before existing entries equal to `x`.
`bisect_right(a, x, lo=0, hi=None)`	Index after existing entries equal to `x`.
`insort_left(a, x, lo=0, hi=None)`	Insert at the left position; return `None`.
`insort_right(a, x, lo=0, hi=None)`	Insert at the right position; return `None`.

bisect aliases bisect_right; insort aliases insort_right. The search interval is [lo, hi), with hi=None meaning len(a). Keep those bounds within the list. There is no key= parameter.

from bisect import bisect_left, bisect_right, insort

scores = [10, 20, 20, 40]
assert bisect_left(scores, 20) == 1
assert bisect_right(scores, 20) == 3
insort(scores, 30)
assert scores == [10, 20, 20, 30, 40]

Implementation: bisect.py.