Binary Search (bisect) in Python

# Python code to demonstrate working
# of binary search in library
from bisect import bisect_left

def BinarySearch(a, x):
    i = bisect_left(a, x)
    if i != len(a) and a[i] == x:
        return i
    else:
        return -1

a  = [1, 2, 4, 4, 8]
x = int(4)
res = BinarySearch(a, x)
if res == -1:
    print(x, "is absent")
else:
    print("First occurrence of", x, "is present at", res)

# Python code to demonstrate working
# of binary search in library
from bisect import bisect_left

def BinarySearch(a, x):
    i = bisect_left(a, x)
    if i:
        return (i-1)
    else:
        return -1

# Driver code
a  = [1, 2, 4, 4, 8]
x = int(7)
res = BinarySearch(a, x)
if res == -1:
    print("No value smaller than ", x)
else:
    print("Largest value smaller than ", x, " is at index ", res)

# Python code to demonstrate working
# of binary search in library
from bisect import bisect_right

def BinarySearch(a, x):
    i = bisect_right(a, x)
    if i != 0 and a[i-1] == x:
        return (i-1)
    else:
        return -1

a  = [1, 2, 4, 4]
x = int(4)
res = BinarySearch(a, x)
if res == -1:
    print(x, "is absent")
else:
    print("Last occurrence of", x, "is present at", res)