第十六節，基本數據類型，字典dict

字典

經常使用操做：
　　索引
　　新增
　　刪除
　　鍵、值、鍵值對
　　循環
　　長度

　　字典由鍵值對組成，由一個鍵（名稱）和 一個值組成，與列表和元組不一樣的是裏面的元素是有鍵的（名稱）

　　因此當要打印字典時，打印字典變量加[鍵]便可

1 #!/usr/bin/env python
2 # -*- coding:utf-8 -*-
3 a = {
4     "zhs":"1",
5     "ls":"2",
6     "ww":"3"
7 }
8 print(a["ls"])
9 #打印出 2 打印出了ls鍵的值

 

建立字典

 1 #!/usr/bin/env python
 2 # -*- coding:utf-8 -*-
 3 a = {"zhs":"1", "ls":"2", "ww":"3"}
 4 #或者
 5 a = dict({"zhs":"1", "ls":"2", "ww":"3"})
 6 #或者
 7 a = {
 8     "zhs":"1",
 9     "ls":"2",
10     "ww":"3"
11 }
12 #通常採用第三中，更容易讀

　　索引

　　打印字典變量加[要打印的鍵]

 1 #!/usr/bin/env python
 2 # -*- coding:utf-8 -*-
 3 a = {
 4     "zhs":"1",
 5     "ls":"2",
 6     "ww":"3"
 7 }
 8 print(a["ls"])
 9 print(a["ww"])
10 #打印出 2 3 打印出了ls和ww鍵的值

　　for循環

 1 #!/usr/bin/env python
 2 # -*- coding:utf-8 -*-
 3 a = {
 4     "zhs":"1",
 5     "ls":"2",
 6     "ww":"3"
 7 }
 8 for b in a:
 9     print(b)
10 #打印出 ww zhs ls 默認循環出的是字典的鍵
11 
12 a = {
13     "zhs":"1",
14     "ls":"2",
15     "ww":"3"
16 }
17 for b in a:
18     print(a[b])
19 #打印出 3 1 2 要打印字典變量加上[自定義循環變量，也就是鍵]才能打印出值

　　keys(self)

　　"""(獲取字典的鍵)"""：返回一個字典的鍵列表

1 #!/usr/bin/env python
2 # -*- coding:utf-8 -*-
3 a = {
4     "zhs":"1",
5     "ls":"2",
6     "ww":"3"
7 }
8 print(a.keys())
9 #打印出 ['ww', 'zhs', 'ls'] 返回字典鍵列表

　　values(self)

　　"""(獲取字典的值)"""：返回一個字典的值列表

1 #!/usr/bin/env python
2 # -*- coding:utf-8 -*-
3 a = {
4     "zhs":"1",
5     "ls":"2",
6     "ww":"3"
7 }
8 print(a.values())
9 #打印出 ['3', '1', '2'] 返回字典值列表

　　items(self)

　　"""(獲取字典裏的鍵和值)"""：返回一個字典的鍵和值列表加元組

1 #!/usr/bin/env python
2 # -*- coding:utf-8 -*-
3 a = {
4     "zhs":"1",
5     "ls":"2",
6     "ww":"3"
7 }
8 print(a.items())
9 #打印出 [('ww', '3'), ('zhs', '1'), ('ls', '2')] 返回字典裏的鍵和值列表加元組

　　(keys：獲取鍵) (values：獲取值) (items：獲取鍵和值) 結合for循環

　　(keys：獲取鍵)結合for循環

 1 #!/usr/bin/env python
 2 # -*- coding:utf-8 -*-
 3 a = {
 4     "zhs":"1",
 5     "ls":"2",
 6     "ww":"3"
 7 }
 8 for b in a.keys():
 9     print(b)
10 #打印出 ww zhs ls 循環出了字典的鍵

　　(values：獲取值)結合for循環

 1 #!/usr/bin/env python
 2 # -*- coding:utf-8 -*-
 3 a = {
 4     "zhs":"1",
 5     "ls":"2",
 6     "ww":"3"
 7 }
 8 for b in a.values():
 9     print(b)
10 #打印出 3 1 2 循環出了字典的值

　　(items：獲取鍵和值)結合for循環

 1 #!/usr/bin/env python
 2 # -*- coding:utf-8 -*-
 3 a = {
 4     "zhs":"1",
 5     "ls":"2",
 6     "ww":"3"
 7 }
 8 for k, v in a.items(): #由於items()獲取的鍵和值，因此循環裏要自定義兩個變量分別表明鍵和值
 9     print(k)
10     print(v)
11 #打印出 ww 3 zhs 1 ls 2 循環出了字典的鍵和值

　　clear(self)

　　"""(清除字典裏的全部內容)"""

 1 #!/usr/bin/env python
 2 # -*- coding:utf-8 -*-
 3 a = {
 4     "zhs":"1",
 5     "ls":"2",
 6     "ww":"3"
 7 }
 8 a.clear()
 9 print(a)
10 #打印出 {} 字典裏是空的

　　get(self, k, d=None)（推薦使用）

　　""" (根據key(鍵)獲取值，若是key(鍵)不存在能夠指定默認值 )"""：若是鍵後面指定了默認值，鍵存在就獲取鍵自身的值，若是鍵不存在就獲取默認值

 1 #!/usr/bin/env python
 2 # -*- coding:utf-8 -*-
 3 a = {
 4     "zhs":"1",
 5     "ls":"2",
 6     "ww":"3"
 7 }
 8 print(a.get("ls"))
 9 #打印出 2 輸出指定鍵的值
10 
11 a = {
12     "zhs":"1",
13     "ls":"2",
14     "ww":"3"
15 }
16 print(a.get("xyz","123")) #xyz鍵不存在，就獲取默認值123
17 #打印出 123 輸出指定鍵的值,若是指定鍵不存在就輸出默認值

　　has_key(self, k)

　　注意：python3版本以上已經取消了

　　""" （：鍵）key：鍵，名稱 """：返回真或者假

1 #!/usr/bin/env python
2 # -*- coding:utf-8 -*-
3 a = {
4     "zhs":"1",
5     "ls":"2",
6     "ww":"3"
7 }
8 print(a.has_key("ls"))
9 #打印出 True 返回真說明字典裏有ls這個鍵

　　判斷字典裏是否有某個key鍵：返回真或者假

　　也能夠判斷字典裏是否有某個值

　　注意：python3版本以上使用這個方法替代已經取消的has_key

　　格式："要判斷的鍵" in 字典變量.keys()

 1 #!/usr/bin/env python
 2 # -*- coding:utf-8 -*-
 3 a = {
 4     "zhs":"1",
 5     "ls":"2",
 6     "ww":"3"
 7 }
 8 b = "ls" in a.keys()
 9 print(b)
10 #打印出 True 返回真說明字典裏有ls這個鍵
11 
12 a = {
13     "zhs":"1",
14     "ls":"2",
15     "ww":"3"
16 }
17 b = "2" in a.values()
18 print(b)
19 #打印出 True 返回真說明字典裏有2這個值

　　update(self, E=None, **F)

　　""" （追加更新）"""要追加更新的變量

　　

 1 #!/usr/bin/env python
 2 # -*- coding:utf-8 -*-
 3 a = {
 4     "zhs":"1",
 5     "ls":"2",
 6     "ww":"3"
 7 }
 8 b = {
 9     "z":"4",
10     "l":"5",
11     "w":"6"
12 }
13 a.update(b)
14 print(a)
15 #打印輸出 {'ww': '3', 'zhs': '1', 'ls': '2', 'w': '6', 'z': '4', 'l': '5'} 將b字典追加更新到了a字典

  追加更新 2

 1 #!/usr/bin/env python
 2 # -*- coding:utf-8 -*-
 3 #這個方法是。若是字典裏存在k4這個鍵就987的值更新給k4鍵，若是不存在k4鍵就在字典裏建立k4鍵值爲987
 4 a = {
 5     "k1":123,
 6     "k2":456,
 7     "k3":789,
 8 }
 9 a["k4"] = 987
10 print(a)

 

　

 

　刪除字典裏的元素

　　　　格式：del 字典變量.[要刪除的元素鍵]

 1 #!/usr/bin/env python
 2 # -*- coding:utf-8 -*-
 3 a = {
 4     "zhs":"1",
 5     "ls":"2",
 6     "ww":"3"
 7 }
 8 del a["ls"]
 9 print(a)
10 #打印輸出 {'ww': '3', 'zhs': '1'} 刪除了ls鍵這個元素

 fromkeys(*args, **kwargs)

"""(查找字典裏一個或多個元素的鍵，將查找的鍵從新指定新的值)要查找的元素鍵，要改變的新值"""

1 #!/usr/bin/env python
2 # -*- coding:utf-8 -*-
3 #fromkeys 查找字典裏一個或多個元素的鍵，將查找的鍵從新指定新的值
4 a = {"k1":123, "k2":456, "k3":789}
5 b = a.fromkeys(["k1", "k2", "k3"], "876")
6 print(b)
7 #輸出 {'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__
        """ 清除內容 """
        """ D.clear() -> None.  Remove all items from D. """
        pass

    def copy(self): # real signature unknown; restored from __doc__
        """ 淺拷貝 """
        """ 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__
        """ 根據key獲取值，d是默認值 """
        """ 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__
        """ 全部項的列表形式 """
        """ D.items() -> list of D's (key, value) pairs, as 2-tuples """
        return []

    def iteritems(self): # real signature unknown; restored from __doc__
        """ 項可迭代 """
        """ 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__
        """ 全部的key列表 """
        """ D.keys() -> list of D's keys """
        return []

    def pop(self, k, d=None): # real signature unknown; restored from __doc__
        """ 獲取並在字典中移除 """
        """
        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__
        """ 獲取並在字典中移除 """
        """
        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__
        """ 若是key不存在，則建立，若是存在，則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__
        """ 全部的值 """
        """ D.values() -> list of D's values """
        return []

    def viewitems(self): # real signature unknown; restored from __doc__
        """ 全部項，只是將內容保存至view對象中 """
        """ 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

索引增長刪除for循環長度項鍵值判斷是否存在某元素更新