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  • 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

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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(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

        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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  • 原文地址:https://www.cnblogs.com/opsedu/p/5498694.html
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