Generic Binary Search in Python

binary_search.py

def binary_search(values, key, lo=0, hi=None, length=None, comp=None):
        """
        This is a binary search function which search for given key in values.
        This is very generic in the sense values and key can be of different type.
        If they are of different type then caller must specify comp function to
        perform comparision between key and values's item.
        :param values:  List of items in which key has to be search
        :param key: search key
        :param lo: start index to begin search
        :param hi: end index where search will be performed
        :param length: length of values
        :param comp: a comparator function which can be used to compare key and values
        :return: -1 if key is not found else index
        """
        assert type(values[0]) == type(key) or comp, "can't be compared"
        assert not (hi and length), "hi, length both can't be specified at the same time"
    
        lo = lo
        if not lo:
            lo = 0
        if hi:
            hi = hi
        elif length:
            hi = length - 1
        else:
            hi = len(values) - 1
    
        while lo <= hi:
            mid = lo + (hi - lo) // 2
            if not comp:
                if values[mid] == key:
                    return mid
                if values[mid] < key:
                    lo = mid + 1
                else:
                    hi = mid - 1
            else:
                val = comp(values[mid], key)
                # 0 -> a == b
                # > 0 -> a > b
                # < 0 -> a < b
                if val == 0:
                    return mid
                if val < 0:
                    lo = mid + 1
                else:
                    hi = mid - 1
        return -1