序列的第一个 truthyfalsy 元素(如果没有,则为最后一个元素)
# First falsy element or last element if all are truthy:
reduce(lambda i, j: i and j, [100, [], 20, 10]) # = []
reduce(lambda i, j: i and j, [100, 50, 20, 10]) # = 10
# First truthy element or last element if all falsy:
reduce(lambda i, j: i or j, [100, [], 20, 0]) # = 100
reduce(lambda i, j: i or j, ['', {}, [], None]) # = None
而不是创建 lambda
函数,通常建议创建一个命名函数:
def do_or(i, j):
return i or j
def do_and(i, j):
return i and j
reduce(do_or, [100, [], 20, 0]) # = 100
reduce(do_and, [100, [], 20, 0]) # = []