浅谈python for循环的巧妙运用(迭代、列表生成式)

#!/usr/bin/env python3
#-*- coding:utf-8 -*-
vlist=['a','b','c']
vtuple=('a','b','c')
vdict={'a': 1, 'b': 2, 'c': 3}
vset={'a','b','c'}
vstr='abc'
for x in vlist:
 print('list:',x)
for x in vtuple:
 print('tuple:',x)
for x in vdict:
 print('dict:',x)
for x in vset:
 print('set:',x)
for x in vstr:
 print('str:',x)

list: a
list: b
list: c
tuple: a
tuple: b
tuple: c
dict: c
dict: a
dict: b
set: a
set: b
set: c
str: a
str: b
str: c

>>> from collections import Iterable
>>> isinstance('abc', Iterable) 
True
>>> isinstance([1,2,3], Iterable) 
True
>>> isinstance(123, Iterable) 

>>> for x, y in [(1, 1), (2, 4), (3, 9)]:
 print(x,y)

1 1
2 4
3 9

>>> for x, y in enumerate(['a', 'b', 'c']):
 print(x, y)

 
0 a
1 b
2 c

#!/usr/bin/env python3
#-*- coding:utf-8 -*-
L=[]
for x in range(1,11):
 L.append(x*x)


print(L)[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

>>> [x*x for x in range(1,11)]


[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

>>> [x*x for x in range(1,11) if x%2==0]
[4, 16, 36, 64, 100]

>>> [m+n for m in 'ABC' for n in'abc']
['Aa', 'Ab', 'Ac', 'Ba', 'Bb', 'Bc', 'Ca', 'Cb', 'Cc']

>>> d={'a': 'A', 'b': 'B', 'c': 'C'}
>>> [k + '=' + v for k,v in d.items()]
['c=C', 'a=A', 'b=B']

#!/usr/bin/env python3
#-*- coding:utf-8 -*-
d={'a': 1, 'b': 2,'c': 3}
for k,v in d.items():
 print(k,'=',v)

>>> L = ['Hello', 'World', 'IBM', 'Apple']
>>> [s.lower() for s in L]
['hello', 'world', 'ibm', 'apple']