python循环技巧

在字典中循环时，关键字和对应的值可以使用 items() 方法同时解读出来。

>>> knights = {'gallahad': 'the pure', 'robin': 'the brave'}
>>> for k, v in knights.items():
...     print k, v
...
gallahad the pure
robin the brave
字典的格式以{key:value}的格式来定义
比如
a = {'name':'xiaoming','age':23}
字典支持嵌套

下面介绍的操作方法用到的例子是:
a = {'name':'xiaoming','age':23}

Python的字典的items(), keys(), values()都返回一个list

>>> dict = { 1 : 2, 'a' : 'b', 'hello' : 'world' }
>>> dict.values()
['b', 2, 'world']
>>> dict.keys()
['a', 1, 'hello']
>>> dict.items()
[('a', 'b'), (1, 2), ('hello', 'world')]
>>>

遍历字典的几种方法：

#!/usr/bin/python 
dict={"a":"apple","b":"banana","o":"orange"} 
 
print "##########dict######################" 
for i in dict: 
        print "dict[%s]=" % i,dict[i] 
 
print "###########items#####################" 
for (k,v) in  dict.items(): 
        print "dict[%s]=" % k,v 
 
print "###########iteritems#################" 
for k,v in dict.iteritems(): 
        print "dict[%s]=" % k,v 
 
print "###########iterkeys,itervalues#######" 
for k,v in zip(dict.iterkeys(),dict.itervalues()): 
        print "dict[%s]=" % k,v 

在序列中循环时，索引位置和对应值可以使用 enumerate() 函数同时得到。

 
>>> for i, v in enumerate(['tic', 'tac', 'toe']):
...     print i, v
...
0 tic
1 tac
2 toe

同时循环两个或更多的序列，可以使用 zip() 整体解读。

>>> questions = ['name', 'quest', 'favorite color']
>>> answers = ['lancelot', 'the holy grail', 'blue']
>>> for q, a in zip(questions, answers):
...     print 'What is your %s?  It is %s.' % (q, a)
...     
What is your name?  It is lancelot.
What is your quest?  It is the holy grail.
What is your favorite color?  It is blue.