Python中的字典及举例

字典

字典是python中的唯一的映射类型（哈希表）

字典对象是可变的，但是字典的键必须使用不可变对象，一个字典中可以使用不同类型的键值。

字典的方法

    keys()

    values()

    items()

举例如下：

    In [10]: dic = {}

    In [11]: type(dic)

    Out[11]: dict

    In [12]: dic = {'a':1,1:123}

    In [13]: dic

    Out[13]: {1: 123, 'a': 1}

    In [14]: dic = {'a':1,1:123,('a','b'):'hello'}

    In [15]: dic = {'a':1,1:123,('a','b'):'hello',[1]:1}

    ---------------------------------------------------------------------------

    TypeError                                 Traceback (most recent call last)

    <ipython-input-15-4fc52e86cb96> in <module>()

    ----> 1 dic = {'a':1,1:123,('a','b'):'hello',[1]:1}

    TypeError: unhashable type: 'list'

    In [16]: len(dic)

    Out[16]: 3

    In [17]: dic.keys()

    Out[17]: ['a', 1, ('a', 'b')]

    In [18]: dic.values()

    Out[18]: [1, 123, 'hello']

    In [19]: dic.get('a')

    Out[19]: 1

    In [20]: dic

    Out[20]: {1: 123, 'a': 1, ('a', 'b'): 'hello'}

    In [21]: dic[1]

    Out[21]: 123

更改字典内value:

    In [22]: dic['a'] = 2

    In [23]: dic

    Out[23]: {1: 123, 'a': 2, ('a', 'b'): 'hello'}

查看是不是在字典里

    In [28]: 'b' in dic

    Out[28]: False

    In [29]: 'a' in dic

    Out[29]: True

    In [30]: dic.has_key('a')

    Out[30]: True

    In [31]: dic.has_key('b')

    Out[31]: False

变为列表：

    In [32]: dic.items()

    Out[32]: [('a', 2), (1, 123), (('a', 'b'), 'hello')]

    In [33]: dic

    Out[33]: {1: 123, 'a': 2, ('a', 'b'): 'hello'}

复制字典：

    In [34]: dic1 = dic.copy()

    In [35]: dic1

    Out[35]: {1: 123, 'a': 2, ('a', 'b'): 'hello'}

    In [36]: dic

    Out[36]: {1: 123, 'a': 2, ('a', 'b'): 'hello'}

删除字典内容:

    In [37]: dic.pop(1)

    Out[37]: 123

    In [38]: dic

    Out[38]: {'a': 2, ('a', 'b'): 'hello'}

    In [39]: dic.pop(2)

    ---------------------------------------------------------------------------

    KeyError                                  Traceback (most recent call last)

    <ipython-input-39-9f97239cddce> in <module>()

    ----> 1 dic.pop(2)

    KeyError: 2

    In [40]:

更新字典，两个字典更新为一个：

    In [40]: dic1 = {1:1,2:2}

    In [41]: dic.update(dic1)

    In [42]: dic1

    Out[42]: {1: 1, 2: 2}

    In [43]: dic

    Out[43]: {1: 1, 2: 2, 'a': 2, ('a', 'b'): 'hello'}

创建字典：

    dic = {}

    dic = dict()

    help(dict)

    dict((['a',1],['b',2]))

    dict(a=1,b=2)

    fromkeys(),字典元素有相同的值时，默认为None.

    ddict = {}.formkeys(('x','y'),100)

    dic.fromkeys(range(100),100)

    In [45]: dic.fromkeys('abc')

    Out[45]: {'a': None, 'b': None, 'c': None}

    In [42]: dic = {}

    In [43]: dic

    Out[43]: {}

    In [44]: dict()

    Out[44]: {}

    In [45]: dict(x=10,y=100)

    Out[45]: {'x': 10, 'y': 100}

    In [46]: dict([('a',10),('b',20)])

    Out[46]: {'a': 10, 'b': 20}

访问字典：

    In [10]: dic={1:1,2:3,3:5}

    In [11]: dic

    Out[11]: {1: 1, 2: 3, 3: 5}

    In [12]: dic[2]

    Out[12]: 3

    In [13]: dic.items()

    Out[13]: [(1, 1), (2, 3), (3, 5)]

for循环访问：

    In [15]: for i in dic:

    ....:     print i,dic[i]

    ....:

    1 1

    2 3

    3 5

     In [18]: for i in dic:

    ....:     print "%s,%s" % (i,dic[i])

    ....:

    1,1

    2,3

    3,5

    In [19]: dic

    Out[19]: {1: 1, 2: 3, 3: 5}

    In [19]: dic

    Out[19]: {1: 1, 2: 3, 3: 5}

    In [21]: for k,v in dic.items():print k,v

    1 1

    2 3

    3 5

字典练习

    写出脚本，根据提示输入内容，并输入到字典中。

1种：

    [root@localhost python]# cat dict.py

    #!/usr/bin/python

    #Author is fengXiaQing

    #date 2017.12.22

    info = {}

    name = raw_input("Please input name:")

    age = raw_input("Please input age:")

    gender = raw_input("Please input (M/F):")

    info['name'] = name

    info['age'] = age

    info['gender'] = gender

    print info

    [root@localhost python]#

    [root@localhost python]# python dict.py

    Please input name:fxq

    Please input age:20

    Please input (M/F):M

    {'gender': 'M', 'age': '20', 'name': 'fxq'}

    [root@localhost python]#

2.种

    #!/usr/bin/python

    #Author is fengXiaQing

    #date 2017.12.22

    info = {}

    name = raw_input("Please input name:")

    age = raw_input("Please input age:")

    gender = raw_input("Please input (M/F):")

    info['name'] = name

    info['age'] = age

    info['gender'] = gender

    print info.items()

    [root@localhost python]# python dict.py

    Please input name:fxq

    Please input age:22

    Please input (M/F):M

    [('gender', 'M'), ('age', '22'), ('name', 'fxq')]

    [root@localhost python]#

3.种

    #!/usr/bin/python

    #Author is fengXiaQing

    #date 2017.12.22

    info = {}

    name = raw_input("Please input name:")

    age = raw_input("Please input age:")

    gender = raw_input("Please input (M/F):")

    info['name'] = name

    info['age'] = age

    info['gender'] = gender

    for i in info.items():

        print i

    print "main end"

    [root@localhost python]# python dict.py

    Please input name:fxq

    Please input age:22

    Please input (M/F):M

    ('gender', 'M')

    ('age', '22')

    ('name', 'fxq')

    main end

    [root@localhost python]#

4.种

    #!/usr/bin/python

    #Author is fengXiaQing

    #date 2017.12.22

    info = {}

    name = raw_input("Please input name:")

    age = raw_input("Please input age:")

    gender = raw_input("Please input (M/F):")

    info['name'] = name

    info['age'] = age

    info['gender'] = gender

    for k,v in info.items():

        print k,v

    print "main end"

    [root@localhost python]# python dict.py

    Please input name:fxq

    Please input age:22

    Please input (M/F):M

    gender M

    age 22

    name fxq

    main end

    [root@localhost python]#

5.种

    #!/usr/bin/python

    #Author is fengXiaQing

    #date 2017.12.22

    info = {}

    name = raw_input("Please input name:")

    age = raw_input("Please input age:")

    gender = raw_input("Please input (M/F):")

    info['name'] = name

    info['age'] = age

    info['gender'] = gender

    for k,v in info.items():

        print "%s:%s" % (k,v)

    print "main end"

    [root@localhost python]# python dict.py

    Please input name:fxq

    Please input age:22    

    Please input (M/F):M

    gender:M

    age:22

    name:fxq

    main end

    [root@localhost python]#

6.种

    #!/usr/bin/python

    #Author is fengXiaQing

    #date 2017.12.22

    info = {}

    name = raw_input("Please input name:")

    age = raw_input("Please input age:")

    gender = raw_input("Please input (M/F):")

    info['name'] = name

    info['age'] = age

    info['gender'] = gender

    for k,v in info.items():

        print "%s" % k

    print "main end"

    [root@localhost python]# python dict.py

    Please input name:fxq

    Please input age:22

    Please input (M/F):M

    gender

    age

    name

    main end

    [root@localhost python]#

练习：

    1. 现有一个字典dict1 保存的是小写字母a-z对应的ASCII码

    dict1 = {'a': 97, 'c': 99, 'b': 98, 'e': 101, 'd': 100, 'g': 103, 'f': 102, 'i': 105, 'h': 104, 'k': 107, 'j': 106, 'm': 109, 'l': 108, 'o': 96, 'n': 110, 'q': 113, 'p': 112, 's': 115, 'r': 114, 'u': 117, 't': 116, 'w': 119, 'v': 118, 'y': 121, 'x': 120, 'z': 122}

    1） 将该字典按照ASCII码的值排序

        print sorted(dict1.iteritems(), key=lambda d:d[1], reverse=False)

    2） 有一个字母的ASCII错了，修改为正确的值，并重新排序

        dict1['o']=111

        print sorted(dict1.iteritems(), key=lambda d:d[1], reverse=False)

    2. 用最简洁的代码，自己生成一个大写字母 A-Z 及其对应的ASCII码值的字典dict2(使用dict，zip，range方法)

        dict2 = dict(zip(string.uppercase,range(65,92)))

        print dict2

    3. 将dict2与第一题排序后的dict1合并成一个dict3

        dict3 = dict(dict1, **dict2)

        # dict3 = dict(dict1, **dict2)等同于下面的两行代码

        # dict3 = dict1.copy()

        # dict3.update(dict2)

        print dict3