for 循环

Python 中的循环有两种,分别是 while 和 for 循环。for 循环常用于遍历字符串、列表、元组、字典、集合等序列类型,逐个获取序列中的各个元素。

语法格式:

for 迭代变量 in 字符串|列表|元组|字典|集合:
    代码块

迭代变量用于存放从序列类型变量中读取出来的元素,所以一般不会在循环中对迭代变量手动赋值;代码块指定是具有相同缩进格式的多行代码(和 while 一样),由于和循环结构联用,因此代码块也成为循环体。

 

 示例:

1 add = "www.taobao.com and www.huawei.com"
2 # for循环,遍历 add 字符串
3 for a in add:
4     print(a, end="")

结果:

www.taobao.com and www.huawei.com

for 循环具体应用:

数值循环:

1 print("计算 1+2+3....+100的结果")
2 # 保存累加结果变量
3 sum = 0
4 # 逐个获取从 1 到 100 这些值,并做累加操作
5 for i in range(101):
6     sum += i
7 print(sum)

结果:

计算 1+2+3....+100的结果
5050

遍历列表:

1 list = [1, 2, 3, 4, 5, 6, 7, 8]
2 for ele in list:
3     print("ele =", ele)

结果:

ele = 1
ele = 2
ele = 3
ele = 4
ele = 5
ele = 6
ele = 7
ele = 8

遍历字典:

1 str = {'Python教程': 'https://www.runoob.com/python3/python3-tutorial.html',\
2        'Shell教程': 'https://www.runoob.com/linux/linux-shell.html',\
3        'Java教程': 'https://www.runoob.com/java/java-tutorial.html'}
4 for i in str:
5     print('i =', i)

结果:

i = Python教程
i = Shell教程
i = Java教程

遍历字典 values()、items() 方法的返回值。

示例:

1 str = {'Python教程': 'https://www.runoob.com/python3/python3-tutorial.html',\
2        'Shell教程': 'https://www.runoob.com/linux/linux-shell.html',\
3        'Java教程': 'https://www.runoob.com/java/java-tutorial.html'}
4 for i in str.items():
5     print('i =', i)

结果:

i = ('Python教程', 'https://www.runoob.com/python3/python3-tutorial.html')
i = ('Shell教程', 'https://www.runoob.com/linux/linux-shell.html')
i = ('Java教程', 'https://www.runoob.com/java/java-tutorial.html')
posted @ 2022-08-22 16:10  南城古  阅读(109)  评论(0编辑  收藏  举报