Binary search sample

binarysearch.py

def binarysesarch(x, a):
    """ binarysesarch implementation
    >>> binarysesarch(1, [1])
    0
    >>> binarysesarch(1, [])
    -1
    >>> binarysesarch(2, [1])
    -1
    >>> binarysesarch(1, [0, 1, 1, 2])
    1
    >>> binarysesarch(2, [0, 1, 2, 2])
    2
    >>> binarysesarch(2, [0, 1, 2])
    2
    >>> binarysesarch(0, [0, 0, 1, 2])
    0
    """
    lo = 0
    hi = len(a)
    while lo < hi:
        mid = lo + (hi - lo)//2
        if x > a[mid]:
            lo = mid + 1
        elif x < a[mid]:
            hi = mid
        elif mid > 0 and a[mid - 1] == x:
            hi = mid
        else:
            return mid
    return -1