Python二分法

def BinarySearch(arr, key):    left, right = 0, len(arr) - 1    mid = 0    while left < right:        mid = int((left+right)/2)        if arr[mid] == key:            return arr[mid]            break        elif arr[mid] > key:            right = mid - 1        else:            left = mid + 1    return -1if __name__ == "__main__":    print BinarySearch([1,2,3,34,56,57,78,87],57)