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基础数据类型(dict字典)

初识字典

标准类型
数字
字符串
列表
字典
元组











  

      字典是Python语言中唯一的映射类型。

  定义:{key1:value1,key2:value2}

        1、键与值用冒号“:”分开;
        2、项与项用逗号“,”分开;
  特性:

      1.key-value结构

        2.key必须可hash、且必须为不可变数据类型、必须唯一

        3.可存放任意多个值、可修改、可以不唯一

        4.无序

字典的创建

  person = {"name": "alex", 'age': 20}
  或
  person = dict(name='seven', age=20)
  person = dict({"name": "egon", 'age': 20})
  person = dict((['name','苑昊'],['文周',18]))
  {}.fromkeys(seq,100) #不指定100默认为None

  注意:

>>> dic={}.fromkeys(['k1','k2'],[])
>>> dic
{'k1': [], 'k2': []}
>>> dic['k1'].append(1)
>>> dic
{'k1': [1], 'k2': [1]} 

 

字典的常用操作

  键、值、键值对

    1、dic.keys() 返回一个包含字典所有KEY的列表;
    2、dic.values() 返回一个包含字典所有value的列表;
    3、dic.items() 返回一个包含所有(键,值)元祖的列表;
    4、dic.iteritems()、dic.iterkeys()、dic.itervalues() 与它们对应的非迭代方法一样,不同的是它们返回一个迭代子,而不是一个列表;

  新增

    1、dic['new_key'] = 'new_value' 

    2、dic.setdefault(key, None) ,如果字典中不存在Key键,由 dic[key] = default 为它赋值;

  删除

    1、dic.pop(key[,default]) 和get方法相似。如果字典中存在key,删除并返回key对应的vuale;如果key不存在,且没有给出default的值,则引发keyerror异常;

    2、dic.clear() 删除字典中的所有项或元素;

  修改

    1、dic['key'] = 'new_value',如果key在字典中存在,'new_value'将会替代原来的value值。

    2、dic.update(dic2) 将字典dic2的键值对添加到字典dic中。

  查看

    1、dic['key'],返回字典中key对应的值,若key不存在字典中,则报错;

    2、adict.get(key, default = None) 返回字典中key对应的值,若key不存在字典中,则返回default的值(default默认为None);   

  循环

  长度

字典的工厂函数

 

class dict(object):
    """
    dict() -> new empty dictionary
    dict(mapping) -> new dictionary initialized from a mapping object's
        (key, value) pairs
    dict(iterable) -> new dictionary initialized as if via:
        d = {}
        for k, v in iterable:
            d[k] = v
    dict(**kwargs) -> new dictionary initialized with the name=value pairs
        in the keyword argument list.  For example:  dict(one=1, two=2)
    """
    def clear(self): # real signature unknown; restored from __doc__
        """ D.clear() -> None.  Remove all items from D. """
        pass

    def copy(self): # real signature unknown; restored from __doc__
        """ D.copy() -> a shallow copy of D """
        pass

    @staticmethod # known case
    def fromkeys(*args, **kwargs): # real signature unknown
        """ Returns a new dict with keys from iterable and values equal to value. """
        pass

    def get(self, k, d=None): # real signature unknown; restored from __doc__
        """ D.get(k[,d]) -> D[k] if k in D, else d.  d defaults to None. """
        pass

    def items(self): # real signature unknown; restored from __doc__
        """ D.items() -> a set-like object providing a view on D's items """
        pass

    def keys(self): # real signature unknown; restored from __doc__
        """ D.keys() -> a set-like object providing a view on D's keys """
        pass

    def pop(self, k, d=None): # real signature unknown; restored from __doc__
        """
        D.pop(k[,d]) -> v, remove specified key and return the corresponding value.
        If key is not found, d is returned if given, otherwise KeyError is raised
        """
        pass

    def popitem(self): # real signature unknown; restored from __doc__
        """
        D.popitem() -> (k, v), remove and return some (key, value) pair as a
        2-tuple; but raise KeyError if D is empty.
        """
        pass

    def setdefault(self, k, d=None): # real signature unknown; restored from __doc__
        """ D.setdefault(k[,d]) -> D.get(k,d), also set D[k]=d if k not in D """
        pass

    def update(self, E=None, **F): # known special case of dict.update
        """
        D.update([E, ]**F) -> None.  Update D from dict/iterable E and F.
        If E is present and has a .keys() method, then does:  for k in E: D[k] = E[k]
        If E is present and lacks a .keys() method, then does:  for k, v in E: D[k] = v
        In either case, this is followed by: for k in F:  D[k] = F[k]
        """
        pass

    def values(self): # real signature unknown; restored from __doc__
        """ D.values() -> an object providing a view on D's values """
        pass

    def __contains__(self, *args, **kwargs): # real signature unknown
        """ True if D has a key k, else False. """
        pass

    def __delitem__(self, *args, **kwargs): # real signature unknown
        """ Delete self[key]. """
        pass

    def __eq__(self, *args, **kwargs): # real signature unknown
        """ Return self==value. """
        pass

    def __getattribute__(self, *args, **kwargs): # real signature unknown
        """ Return getattr(self, name). """
        pass

    def __getitem__(self, y): # real signature unknown; restored from __doc__
        """ x.__getitem__(y) <==> x[y] """
        pass

    def __ge__(self, *args, **kwargs): # real signature unknown
        """ Return self>=value. """
        pass

    def __gt__(self, *args, **kwargs): # real signature unknown
        """ Return self>value. """
        pass

    def __init__(self, seq=None, **kwargs): # known special case of dict.__init__
        """
        dict() -> new empty dictionary
        dict(mapping) -> new dictionary initialized from a mapping object's
            (key, value) pairs
        dict(iterable) -> new dictionary initialized as if via:
            d = {}
            for k, v in iterable:
                d[k] = v
        dict(**kwargs) -> new dictionary initialized with the name=value pairs
            in the keyword argument list.  For example:  dict(one=1, two=2)
        # (copied from class doc)
        """
        pass

    def __iter__(self, *args, **kwargs): # real signature unknown
        """ Implement iter(self). """
        pass

    def __len__(self, *args, **kwargs): # real signature unknown
        """ Return len(self). """
        pass

    def __le__(self, *args, **kwargs): # real signature unknown
        """ Return self<=value. """
        pass

    def __lt__(self, *args, **kwargs): # real signature unknown
        """ Return self<value. """
        pass

    @staticmethod # known case of __new__
    def __new__(*args, **kwargs): # real signature unknown
        """ Create and return a new object.  See help(type) for accurate signature. """
        pass

    def __ne__(self, *args, **kwargs): # real signature unknown
        """ Return self!=value. """
        pass

    def __repr__(self, *args, **kwargs): # real signature unknown
        """ Return repr(self). """
        pass

    def __setitem__(self, *args, **kwargs): # real signature unknown
        """ Set self[key] to value. """
        pass

    def __sizeof__(self): # real signature unknown; restored from __doc__
        """ D.__sizeof__() -> size of D in memory, in bytes """
        pass

    __hash__ = None
dict的工厂函数

 

posted @ 2017-06-04 12:08  Eva_J  阅读(488)  评论(0编辑  收藏