Python字典方法总结
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1.清空字典中元素清空,dict变为{}
L.clear()-> None. Remove all items from L
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>>> 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
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>>> 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.
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>>> 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.
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>>> 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
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>>> 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
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>>> 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
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>>> 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
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>>> 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.
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>>> 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
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>>> 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()
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>>> 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(…)
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>>> L = { ‘book‘ : 45 , ‘apple‘ : 13 } >>> L.values() [ 45 , 13 ] |
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