python基础语法---三大流程控制之for循环

循环控制之for循环：
for循环一般用于循环列表、字典、元组与集合，字符串也可以循环，取出的是字符
1、列表循环

1 names=['zj','xiaowang','laoli','laowang','zhangsan']
2 
3 n=0
4 while n < len(names):
5     print(names[n])
6     n+=1

列表举例

2、字典循环---取出的是key

1 info={'name':'zj','age':18,'sex':'male'}
2 
3 for k in info: 
4     print(k,info[k])

字典举例

3、range循环与步长

 1 for i in range(1,10):
 2     print(i)
 3 
 4 for i in range(10): #默认的起始位置是0
 5     print(i)
 6 
 7 for i in range(1,10,2): #1 3  5  7  9
 8     print(i)
 9 
10 names=['zj','xw','ww','lw','xz']
11 for i in range(len(names)):
12     print(i,names[i])

例子

4、for嵌套

1 for i in range(5):
2     print('========>第一层: %s' %i)
3     for j in range(3):
4         print('         第二层: %s' %j)

for嵌套

5、for+break---break用于退出本层循环

1 names=['zj','xw','ww','lw','xz']
2 for n in names:
3     if n == 'zj':
4         break
5     print(n)

if+break

6、for+continue---continue用于退出本次循环，继续下一次循环

1 names=['zj','xw','ww','lw','xz']
2 for n in names:
3     if n == 'zj':
4         continue
5     print(n)

for+continue

7、for+else--用法同while

1 names=['zj','xw','ww','lw','xz']
2 for n in names:
3     # if n == 'zj':
4     #     break
5     print(n)
6 else:
7     print('=====>')

for+else