Helpers to find entries in a sorted list (using python bisect module)

SortedListHelpers.py

from bisect import *

##### HELPER FUNCTIONS FROM PYTHON DOCUMENTATION #####

def index(a, x):
    'Locate the leftmost value exactly equal to x'
    i = bisect_left(a, x)
    if i != len(a) and a[i] == x:
        return i
    raise ValueError

def find_lt(a, x):
    'Find rightmost value less than x'
    i = bisect_left(a, x)
    if i:
        return a[i-1]
    raise ValueError

def find_le(a, x):
    'Find rightmost value less than or equal to x'
    i = bisect_right(a, x)
    if i:
        return a[i-1]
    raise ValueError

def find_gt(a, x):
    'Find leftmost value greater than x'
    i = bisect_right(a, x)
    if i != len(a):
        return a[i]
    raise ValueError

def find_ge(a, x):
    'Find leftmost item greater than or equal to x'
    i = bisect_left(a, x)
    if i != len(a):
        return a[i]
    raise ValueError

##### HELPERS TO RETURN INDICES #####

def index_left(a, x):
    'Locate the leftmost value exactly equal to x'
    return index(a, x)

def index_right(a, x):
    'Locate the rightmost value exactly equal to x'
    i = bisect_right(a, x)
    if i>0 and a[i-1] == x:
        return i-1
    raise ValueError

def find_lt_index(a, x):
    'Find index of rightmost value less than x'
    i = bisect_left(a, x)
    if i:
        return i-1
    raise ValueError

def find_le_index(a, x):
    'Find index of rightmost value less than or equal to x'
    i = bisect_right(a, x)
    if i:
        return i-1
    raise ValueError

def find_gt_index(a, x):
    'Find index of leftmost value greater than x'
    i = bisect_right(a, x)
    if i != len(a):
        return i
    raise ValueError

def find_ge_index(a, x):
    'Find index of leftmost item greater than or equal to x'
    i = bisect_left(a, x)
    if i != len(a):
        return i
    raise ValueError