Python编程：从入门到实践 学习笔记 基础知识（四）字典

写在前面：原书地址：http://www.ituring.com.cn/book/1861（图灵社区）

                 本博客是对书籍学习而进行总结的学习笔记，如有侵权行为必删。

1.字典

在Python语言中，字典是一系列 “键-值对”。 每个键都要与一个值产生联系，这样就可以使用键来访问与之相关联的值。

键和值之间用冒号隔开，键-值对之间使用逗号。

ads = {'color': 'red' , 'points' = '5'}

访问字典中的值

ads = {'color': 'red' , 'points' = '5'}
print(ads['color'])


#输出结果
red

字典是一种动态结构，可以随时添加键-值对。

ads = {'color': 'red' , 'points' = '5'}
ads['x_position'] = 5
ads['y_position'] = 20

print(ads)


#输出结果
{'color': 'red' , 'points' = '5' ，'x_poition' = 5 , 'y_position' = 20}

在空字典中添加内容

ads = {}
ads['color'] = 'green'
ads['point'] = 5

print(ads)

#输出结果
{'color': 'green' , 'points' = '5'}

修改字典中内容

ads = {'color' : 'red'}
print("this is a" + ads['color'] + "pen" + ".")

ads['color'] = "green"
print("now is a" + ads['color'] + "pen" + ".")

#输出结果
this is a red pen.
now is a green pen.

删除键-值对

ads = {'color':'red' , 'points': 5}
del ads['color']
print(ads)

#输出结果
{'points': 5 }

类似对象组成 的字典

缩进四个空格。

favorite_foods = {
    'mama':'egg',
    'baba':'milk',
    'tom':'suger',
    'yuyu':'tomato',
    }

2.遍历字典

遍历字典中的键 ：keys( )         按顺序遍历 sored( )

遍历字典中的值 ：values( )

favorite_foods = {
    'mama':'egg',
    'baba':'milk',
    'tom':'suger',
    'yuyu':'tomato',
    }

for name in sorted(favorite_foods.keys()):
print(name.title() + ",thank you.")

#输出结果
Mama,thank you.
Baba,thank you.
Tom,thank you.
Yuyu,thank you.


favorite_foods = {
    'mama':'egg',
    'baba':'milk',
    'tom':'suger',
    'yuyu':'tomato',
    }

print("what is you like ?")
for food in favorite_foods.values():
print("food.title()")


#输出结果
what is you like ?
Egg
Milk
Suger
Tomato

3.嵌套

字典存储在列表中，或者列表存储在字典中，

1.字典列表

ads_0 = {'color' : 'red' , 'points' : 5}
ads_1 = {'color' : 'blue' , 'points' : 15}
ads_2 = {'color' : 'green' , 'points' : 25}

adss = [ads_0 , ads_1 , ads_2]
for af in adss:
print(af)

# 输出结果
{'color' : 'red' , 'points' : 5}
{'color' : 'blue' , 'points' : 15}
{'color' : 'green' , 'points' : 25}

2.字典存储在列表中

favorite_languages = {
    'mama' : ['python', 'go'],
    'baba' : ['c' , 'java'],
    'tom' : ['php' , 'c'],
    'yuyu' : ['c' , 'swift'],
    }

for name, languages in favorite_languages.items():
    print("\n" + name.title() + "'s favorite languages are:")
    for language in languages:
        print("\t" + language.title())

#输出结果
Mama's favorite languages are:
     Python
     Go 
Baba's favorite languages are:
     C
     Java
Tom's favorite languages are:
     Php
     C
Yuyu's favorite languages are:
     C
     Swift 

3.字典中存储字典

users = {
    'a' : {
        'first': 'he',
        'last' : 'is',
        'location' : 'kui',
        },
    'b' : {
        'first': 'she',
        'last' : 'was',
        'location' : 'hui',
        }, 

    }

for username, user_info in users.items():
    print("\nUsername:" + username)
    full_name = user_info['first'] + " " + user_info['last']
    location = user_info['location']
 
    print("\tFull name: " + full_name.title())
    print("\tLocation: " + location.title())

#输出结果
 
Username: a
     Full name: he is
     Location: kui
Username: b
     Full name: she was
     Location: hui