from bisect import bisect_leftdef binary_search(a, x, lo=0, hi=None): # can't use a to specify default for hi hi = hi if hi is not None else len(a) # hi defaults to len(a) pos = bisect_left(a, x, lo, hi) # find insertion position return pos if pos != hi and a[pos] == x else -1 # don't walk off the end
