a = [1,5,6,9,10,-1] def max_value (a,b): return a if a > b else b def max_sequence(x): result = x[0] for element in x: result = max_value(result, element) return result print(max_sequence(a)) def min_value(a,b): return b if a > b else a def min_sequence(x): result = x[0] for element in x: result = min_value(result, element) return result print(min_sequence(a)) def reduce1(fn, x): result = x[0] for element in x: result = fn(result, element) return result def reduce2(fn, x, init): # change to fn result = init for element in x: result = fn(result, element) return result def sum1(a,b): return a + b print(reduce1(max_value, a)) print(reduce1(min_value, a)) print(reduce2(sum1, a, 0)) # there is a bug, add an initial value at the end print(reduce2(max_value, a, a[0])) #=============================================== from functools import reduce print(reduce(sum1,a,0)) # same as line 32; sum1 is a callback function; a is a list