Python字典方法总结
1.清空字典中元素清空，dict变为{}
L.clear()-> None. Remove all items from L
>>> L ={'shaw':23,'sam':36,"eric":40}
>>> L.clear()
>>> print L
{}
2.返回一个字典的浅复制
L.copy()-> a shallow copy of L
>>> L ={'shaw':23,'sam':36,"eric":40}
>>> L.copy()
{'shaw': 23, 'sam': 36,'eric': 40}
3.用于创建一个新字典，以序列seq中元素做字典的键，value为字典所有键对应的初始值(默认为“None”)
Lict.fromkeys(S[,v])-> New Lict with keys from S and values equal to v. v defaults toNone.
>>> seq =('shaw','sam','stiven')
>>> name =dict.fromkeys(seq)
>>> print"listone :{}".format(name)
listone :{'stiven': None,'shaw': None, 'sam': None}
>>> name =dict.fromkeys(seq,1000)
>>> print"listone :{}".format(name)
listone :{'stiven': 1000,'shaw': 1000, 'sam': 1000}
4．返回指定键的值，如果值不在字典中返回默认值(None)
D.get(k[,d])-> D[k] if k in D, else d. d defaultsto None.
>>> L ={'shaw':23,'sam':36,"eric":40}
>>> L.get('shaw')
23
>>> printL.get('stiven')
None
5．用于判断键是否存在于字典中，如果键在字典dict里返回true，否则返回false
L.has_key(k) -> True if D has a key k,else False
>>> L ={'shaw':23,'sam':36,"eric":40}
>>> L.has_key('sam')
True
>>>L.has_key('linux')
False
6.以列表的方式返回可遍历的(键, 值) 元组（键值对）
L.items()-> list of D's (key, value) pairs, as 2-tuples
>>> L ={'shaw':23,'sam':36,"eric":40}
>>> L.items()
[('shaw', 23), ('sam', 36),('eric', 40)]
7.以列表的方式返回一个字典所有的键
L.keys()-> a set-like object providing a view on L's keys
>>> L ={'shaw':23,'sam':36,"eric":40}
>>> L.keys()
['shaw', 'sam', 'eric']
8.删除某个键值对
D.pop(k[,d])-> v, remove specified key and return the corresponding value. If key is notfound, d is returned if given, otherwise KeyError is raised
>>> L ={'shaw':23,'sam':36,"eric":40}
>>> L.pop('sam')
36
>>> L
{'shaw': 23, 'eric': 40}
9.默认删除字典中第一个键值对
D.popitem()-> (k, v), remove and return some (key, value) pair as a 2-tuple; but raise KeyError if D is empty.
>>> L ={'shaw':23,'sam':36,"eric":40}
>>> L.popitem()
('shaw', 23)
>>> L
{'sam': 36, 'eric': 40}
10. setdefault()方法和get()方法类似，如果键不已经存在于字典中，将会添加键并将值设为默认值（如果dict中已有a,则不会被覆盖）
D.setdefault(k[,d]) ->D.get(k,d), also set D[k]=d if k not in D
>>> L ={'shaw':23,'sam':36,"eric":40}
>>>L.setdefault('stiven')
>>> L
{'stiven': None, 'shaw': 23,'sam': 36, 'eric': 40}
>>>L.setdefault('mira',65)
65
>>> L
{'stiven': None, 'mira': 65,'shaw': 23, 'sam': 36, 'eric': 40}
>>>L.setdefault('shaw',18)
23
>>> L
{'stiven': None, 'mira': 65,'shaw': 23, 'sam': 36, 'eric': 40}
11.把字典dict2的键/值对更新到dict里
L.update()
>>> L ={'shaw':23,'sam':36,"eric":40}
>>> A ={'book':45,'apple':13}
>>> L.update(A)
>>> L
{'book': 45, 'apple': 13,'shaw': 23, 'sam': 36, 'eric': 40}
12．返回dic所有的值
L.values(…)
>>> L = {'book':45,'apple':13}
>>> L.values()
[45, 13]