python学习笔记循环使用

循环使用

一、while 注意缩进。

循环1

>>> while True:

word = input(‘please enter a word:‘)

if not word:

break

print(‘The word was ‘+word)

结果

please enter a word:ddd

The word was ddd

please enter a word:ddd

The word was ddd

please enter a word:rrr

The word was rrr

循环2

word=‘‘

while not word:

word = input(‘name:‘)

print("hell, %s"%word)

结果

name:hhh

hell, hhh

二、for循环使用

1、列表输出

words = [‘a‘,‘b‘,‘c‘,‘d‘]

for word in words:

print(word， )

输出

a

b

c

d

2、遍历字典元素。

d = {‘a1‘: 33, ‘port6‘: 55, ‘a2‘: ‘ddd‘}

for key in d:

print("key:%s"%key),

print("value: %s"%d[key])

输出结果，注意顺序不是从字典左到右输出。随机的。

key:a2

value: ddd

key:a1

value: 33

key:port6

value: 55

注意和c语言一样跳出循环式break，继续下一次循环式continue。

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