python - Udacity 深入计算机科学 (Python) 第 2 课 PS 印章 - 输出包括 "None"

Question

这个问题已经有答案了:

Why is "None" printed after my function's output? (7 个回答)

已关闭 6 年前。

我已经在互联网上搜索并尝试了代码的变体，但我只是不明白为什么当我在 Udacity 计算机科学入门的第 2 课中研究 PS 2 时，结果之间的输出为“无” .

这是 PS 和我当前的状态:

# Define a procedure, stamps, which takes as its input a positive integer in
# pence and returns the number of 5p, 2p and 1p stamps (p is pence) required 
# to make up that value. The return value should be a tuple of three numbers 
# (that is, your return statement should be followed by the number of 5p,
# the number of 2p, and the nuber of 1p stamps).
#
# Your answer should use as few total stamps as possible by first using as 
# many 5p stamps as possible, then 2 pence stamps and finally 1p stamps as 
# needed to make up the total.
#


def stamps(n):
    if n > 0:
        five = n / 5
        two = n % 5 / 2
        one = n % 5 % 2
        print (five, two, one)
    else:
        print (0, 0, 0)


print stamps(8)
#>>> (1, 1, 1)  # one 5p stamp, one 2p stamp and one 1p stamp
print stamps(5)
#>>> (1, 0, 0)  # one 5p stamp, no 2p stamps and no 1p stamps
print stamps(29)
#>>> (5, 2, 0)  # five 5p stamps, two 2p stamps and no 1p stamps
print stamps(0)
#>>> (0, 0, 0) # no 5p stamps, no 2p stamps and no 1p stamps

产生输出:

(1, 1, 1)
None
(1, 0, 0)
None
(5, 2, 0)
None
(0, 0, 0)
None

谁能解释一下“无”从何而来？

Answer 1

您正在调用打印结果的函数，然后打印该函数的返回值，即None。

您应该选择一种显示数据的方法。要么只在函数内部打印:

def stamps(n):
    if n > 0:
        five = n / 5
        two = n % 5 / 2
        one = n % 5 % 2
        print five, two, one
    else:
        print 0, 0, 0

stamps(8)
stamps(5)
stamps(29)
stamps(0)

或者使用return:

def stamps(n):
    if n > 0:
        five = n / 5
        two = n % 5 / 2
        one = n % 5 % 2
        return five, two, one
    else:
        return 0, 0, 0


print stamps(8)
print stamps(5)
print stamps(29)
print stamps(0)