Binary Search using bisect Three methods

#User function template for Python
#Method 1
from bisect import bisect_left as bs
class Solution:
    def binarysearch(self, a, n, k):
        idx=bs(arr,k)
        if idx<n and a[idx]==k:
            return idx
        else:return -1

#Method 2
from bisect import bisect_right as bs
class Solution:
    def binarysearch(self, a, n, k):
        idx=bs(arr,k)
        if idx<n and a[idx]==k:
            return idx
        if idx>1 and a[idx-1]==k:
            return idx-1
        return -1

#Method 3
from bisect import bisect_left as bl,bisect_right as br
class Solution:
    def binarysearch(self, a, n, k):
        x,y=bl(a,k),br(a,k)
        if x==y:return -1
        else:
            return x