第十六节，基本数据类型，字典dict

字典

常用操作：
　　索引
　　新增
　　删除
　　键、值、键值对
　　循环
　　长度

　　字典由键值对组成，由一个键（名称）和 一个值组成，与列表和元组不同的是里面的元素是有键的（名称）

　　所以当要打印字典时，打印字典变量加[键]即可

 #!/usr/bin/env python
 # -*- coding:utf-8 -*-
 a = {
     "zhs":"",
     "ls":"",
     "ww":""
 }
 print(a["ls"])
 #打印出 2 打印出了ls键的值

创建字典

 #!/usr/bin/env python
 # -*- coding:utf-8 -*-
 a = {"zhs":"", "ls":"", "ww":""}
 #或者
 a = dict({"zhs":"", "ls":"", "ww":""})
 #或者
 a = {
     "zhs":"",
     "ls":"",
     "ww":""
 }
 #一般采用第三中，更容易读

　　索引

　　打印字典变量加[要打印的键]

 #!/usr/bin/env python
 # -*- coding:utf-8 -*-
 a = {
     "zhs":"",
     "ls":"",
     "ww":""
 }
 print(a["ls"])
 print(a["ww"])
 #打印出 2 3 打印出了ls和ww键的值

　　for循环

 #!/usr/bin/env python
 # -*- coding:utf-8 -*-
 a = {
     "zhs":"",
     "ls":"",
     "ww":""
 }
 for b in a:
     print(b)
 #打印出 ww zhs ls 默认循环出的是字典的键

 a = {
     "zhs":"",
     "ls":"",
     "ww":""
 }
 for b in a:
     print(a[b])
 #打印出 3 1 2 要打印字典变量加上[自定义循环变量，也就是键]才能打印出值

　　keys(self)

　　"""(获取字典的键)"""：返回一个字典的键列表

 #!/usr/bin/env python
 # -*- coding:utf-8 -*-
 a = {
     "zhs":"",
     "ls":"",
     "ww":""
 }
 print(a.keys())
 #打印出 ['ww', 'zhs', 'ls'] 返回字典键列表

　　values(self)

　　"""(获取字典的值)"""：返回一个字典的值列表

 #!/usr/bin/env python
 # -*- coding:utf-8 -*-
 a = {
     "zhs":"",
     "ls":"",
     "ww":""
 }
 print(a.values())
 #打印出 ['3', '1', '2'] 返回字典值列表

　　items(self)

　　"""(获取字典里的键和值)"""：返回一个字典的键和值列表加元组

 #!/usr/bin/env python
 # -*- coding:utf-8 -*-
 a = {
     "zhs":"",
     "ls":"",
     "ww":""
 }
 print(a.items())
 #打印出 [('ww', '3'), ('zhs', '1'), ('ls', '2')] 返回字典里的键和值列表加元组

　　(keys：获取键) (values：获取值) (items：获取键和值) 结合for循环

　　(keys：获取键)结合for循环

 #!/usr/bin/env python
 # -*- coding:utf-8 -*-
 a = {
     "zhs":"",
     "ls":"",
     "ww":""
 }
 for b in a.keys():
     print(b)
 #打印出 ww zhs ls 循环出了字典的键

　　(values：获取值)结合for循环

 #!/usr/bin/env python
 # -*- coding:utf-8 -*-
 a = {
     "zhs":"",
     "ls":"",
     "ww":""
 }
 for b in a.values():
     print(b)
 #打印出 3 1 2 循环出了字典的值

　　(items：获取键和值)结合for循环

 #!/usr/bin/env python
 # -*- coding:utf-8 -*-
 a = {
     "zhs":"",
     "ls":"",
     "ww":""
 }
 for k, v in a.items(): #因为items()获取的键和值，所以循环里要自定义两个变量分别代表键和值
     print(k)
     print(v)
 #打印出 ww 3 zhs 1 ls 2 循环出了字典的键和值

　　clear(self)

　　"""(清除字典里的所有内容)"""

 #!/usr/bin/env python
 # -*- coding:utf-8 -*-
 a = {
     "zhs":"",
     "ls":"",
     "ww":""
 }
 a.clear()
 print(a)
 #打印出 {} 字典里是空的

　　get(self, k, d=None)（推荐使用）

　　""" (根据key(键)获取值，如果key(键)不存在可以指定默认值 )"""：如果键后面指定了默认值，键存在就获取键自身的值，如果键不存在就获取默认值

 #!/usr/bin/env python
 # -*- coding:utf-8 -*-
 a = {
     "zhs":"",
     "ls":"",
     "ww":""
 }
 print(a.get("ls"))
 #打印出 2 输出指定键的值

 a = {
     "zhs":"",
     "ls":"",
     "ww":""
 }
 print(a.get("xyz","")) #xyz键不存在，就获取默认值123
 #打印出 123 输出指定键的值,如果指定键不存在就输出默认值

　　has_key(self, k)

　　注意：python3版本以上已经取消了

　　""" （：键）key：键，名称 """：返回真或者假

 #!/usr/bin/env python
 # -*- coding:utf-8 -*-
 a = {
     "zhs":"",
     "ls":"",
     "ww":""
 }
 print(a.has_key("ls"))
 #打印出 True 返回真说明字典里有ls这个键

　　判断字典里是否有某个key键：返回真或者假

　　也可以判断字典里是否有某个值

　　注意：python3版本以上使用这个方法替代已经取消的has_key

　　格式："要判断的键" in 字典变量.keys()

 #!/usr/bin/env python
 # -*- coding:utf-8 -*-
 a = {
     "zhs":"",
     "ls":"",
     "ww":""
 }
 b = "ls" in a.keys()
 print(b)
 #打印出 True 返回真说明字典里有ls这个键

 a = {
     "zhs":"",
     "ls":"",
     "ww":""
 }
 b = "" in a.values()
 print(b)
 #打印出 True 返回真说明字典里有2这个值

　　update(self, E=None, **F)

　　""" （追加更新）"""要追加更新的变量

　　

 #!/usr/bin/env python
 # -*- coding:utf-8 -*-
 a = {
     "zhs":"",
     "ls":"",
     "ww":""
 }
 b = {
     "z":"",
     "l":"",
     "w":""
 }
 a.update(b)
 print(a)
 #打印输出 {'ww': '3', 'zhs': '1', 'ls': '2', 'w': '6', 'z': '4', 'l': '5'} 将b字典追加更新到了a字典

  追加更新 2

 #!/usr/bin/env python
 # -*- coding:utf-8 -*-
 #这个方法是。如果字典里存在k4这个键就987的值更新给k4键，如果不存在k4键就在字典里创建k4键值为987
 a = {
     "k1":123,
     "k2":456,
     "k3":789,
 }
 a["k4"] = 987
 print(a)

　

　删除字典里的元素

　　　　格式：del 字典变量.[要删除的元素键]

 #!/usr/bin/env python
 # -*- coding:utf-8 -*-
 a = {
     "zhs":"",
     "ls":"",
     "ww":""
 }
 del a["ls"]
 print(a)
 #打印输出 {'ww': '3', 'zhs': '1'} 删除了ls键这个元素

fromkeys(*args, **kwargs)

"""(查找字典里一个或多个元素的键，将查找的键重新指定新的值)要查找的元素键，要改变的新值"""

 #!/usr/bin/env python
 # -*- coding:utf-8 -*-
 #fromkeys 查找字典里一个或多个元素的键，将查找的键重新指定新的值
 a = {"k1":123, "k2":456, "k3":789}
 b = a.fromkeys(["k1", "k2", "k3"], "")
 print(b)
 #输出 {'k2': '876', 'k3': '876', 'k1': '876'}

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__
        """ 清除内容 """
        """ D.clear() -> None.  Remove all items from D. """
        pass

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

    @staticmethod # known case
    def fromkeys(S, v=None): # real signature unknown; restored from __doc__
        """
        dict.fromkeys(S[,v]) -> New dict with keys from S and values equal to v.
        v defaults to None.
        """
        pass

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

    def has_key(self, k): # real signature unknown; restored from __doc__
        """ 是否有key """
        """ D.has_key(k) -> True if D has a key k, else False """
        return False

    def items(self): # real signature unknown; restored from __doc__
        """ 所有项的列表形式 """
        """ D.items() -> list of D's (key, value) pairs, as 2-tuples """
        return []

    def iteritems(self): # real signature unknown; restored from __doc__
        """ 项可迭代 """
        """ D.iteritems() -> an iterator over the (key, value) items of D """
        pass

    def iterkeys(self): # real signature unknown; restored from __doc__
        """ key可迭代 """
        """ D.iterkeys() -> an iterator over the keys of D """
        pass

    def itervalues(self): # real signature unknown; restored from __doc__
        """ value可迭代 """
        """ D.itervalues() -> an iterator over the values of D """
        pass

    def keys(self): # real signature unknown; restored from __doc__
        """ 所有的key列表 """
        """ D.keys() -> list of D's keys """
        return []

    def pop(self, k, d=None): # real signature unknown; restored from __doc__
        """ 获取并在字典中移除 """
        """
        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__
        """ 获取并在字典中移除 """
        """
        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__
        """ 如果key不存在，则创建，如果存在，则返回已存在的值且不修改 """
        """ 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
        """ 更新
            {'name':'alex', 'age': 18000}
            [('name','sbsbsb'),]
        """
        """
        D.update([E, ]**F) -> None.  Update D from dict/iterable E and F.
        If E present and has a .keys() method, does:     for k in E: D[k] = E[k]
        If E present and lacks .keys() method, 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__
        """ 所有的值 """
        """ D.values() -> list of D's values """
        return []

    def viewitems(self): # real signature unknown; restored from __doc__
        """ 所有项，只是将内容保存至view对象中 """
        """ D.viewitems() -> a set-like object providing a view on D's items """
        pass

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

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

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

    def __contains__(self, k): # real signature unknown; restored from __doc__
        """ D.__contains__(k) -> True if D has a key k, else False """
        return False

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

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

    def __getattribute__(self, name): # real signature unknown; restored from __doc__
        """ x.__getattribute__('name') <==> x.name """
        pass

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

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

    def __gt__(self, y): # real signature unknown; restored from __doc__
        """ x.__gt__(y) <==> x>y """
        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): # real signature unknown; restored from __doc__
        """ x.__iter__() <==> iter(x) """
        pass

    def __len__(self): # real signature unknown; restored from __doc__
        """ x.__len__() <==> len(x) """
        pass

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

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

    @staticmethod # known case of __new__
    def __new__(S, *more): # real signature unknown; restored from __doc__
        """ T.__new__(S, ...) -> a new object with type S, a subtype of T """
        pass

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

    def __repr__(self): # real signature unknown; restored from __doc__
        """ x.__repr__() <==> repr(x) """
        pass

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

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

    __hash__ = None

dict

字典的功能

索引
增加
删除
for循环
长度
项
键
值
判断是否存在某元素
更新