一直以來以爲reduce是這樣用的
def add(x, y): return x+y li = [1,2,3,4,5,6] sum = reduce(add,li)
這樣等同於 sum=add(add...add(1,2))
但是查看源碼可以看到reduce可以有3個參數
def reduce(function, sequence, initial=None): pass
一直沒有關心inital參數是什麼作用,網上有人給出源碼,說是官方文檔,但是這段代碼是有問題的,
def reduc(functon,iterable,initializer=None): it = iter(iterable) if initializer is None: try: initializer = next(it) except StopIteration: raise TypeError('reduce of empty') accum_value = initializer for x in iterable: accum_value = functon(accum_value, x) return accum_value
其實我只是想弄清楚傳參過程
def handle(request,data): return request+data lis = [1,2,3,4] sum = reduce(handle,lis,10)
第一次調用handle(10,1) request=10,data=1