Python中的字典及举例-原创手记-慕课网

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