python高级特性-迭代

概述

for  v   in d.values():

for k,v  in d.items():

for  a    in 'adfa':

#判断对象是否可迭代

from collections import Iterable

isinstance('abc',Iterable)

#添加下标

for x,y in enumerate([(1,1),(2,3),(4,5)]):

详解

1.迭代list

>>> d={'a':1,'b':2,'c':3}

#输出values

>>> for v in d.values():
... print v
...
1
3
2

#同时输出key，value

>>> for k, v in d.items():

...      print k,v

...

#输出

a 1

c 3

b 2

2.字符串迭代

>>> for a in 'adfa':

...      print a

...

a

d

f

a

3.判断一个对象是否可迭代

>>>from collections import Iterable

#判断字符串是否可迭代

>>>isinstance('abc',Iterable)

#输出

True
#判断list是否可迭代

>>>isinstance([1,2,3],Iterable)

#输出

True
#判断整数是否可迭代

>>> isinstance(12345,Iterable)
False

4.对list实现下标循环

>>> for i,value in enumerate(['a','b','c']):

...      print(i,value)

...

(0, 'a')

(1, 'b')

(2, 'c')

>>> for i,value in enumerate(['a','b','c']):

...      print  i,value

...

0 a

1 b

2 c

>>> for x,y in [(1,1),(2,3),(4,5)]:

...      print x,y

...

1 1

2 3

4 5