python基础知识之字典(Dict)

 一、字典的基本操作

1.定义字典 

字典也是一个列表型的数据结构，字典的数据是用“{ }”装的（列表：[ ]，元组：( )），字典的元素是一一对应的关系“key-value”。

格式：

Dictname={ key1:value1,...,key2:value2}    

#value是任何的python的对象

#字典的元素数量也是用len()函数

多说无益，直接看例子比较清晰：

实例： 

flower={'rose':10,'orchid':16,'carnation':8}
tea={'红茶':30,'绿茶':20,'茉莉花茶':40}
print(flower)
print(tea)
print("字典flower的元素数量是：",len(flower))
print("字典的数据类型：",type(tea))

2.建立空字典

实例：

print("``````````````````````````````````````````````````````````")
flower={}
flower['rose']=13
flower['orchid']=16
print(flower)
print("``````````````````````````````````````````````````````````")

3.列出字典元素的值 

格式：

flower【'rose'】

#注意列出字典元素的值要用中括号哦“[ ]”

#上面语句表达的意思是字典 flower 的 rose（key）的对应 10（value）值。

实例： 

print("``````````````````````````````````````````````````````````")
flower={'rose':10,'orchid':16,'carnation':8}
tea={'红茶':30,'绿茶':20,'茉莉花茶':40}
print("一支玫瑰的价钱是：",flower['rose'])
print("红茶一袋的价钱是：",tea['红茶'])
print("``````````````````````````````````````````````````````````")

如果有两个“rose”，两个“红茶”呢，元素对应的值（value）是哪个呢？

print("``````````````````````````````````````````````````````````")
flower={'rose':10,'orchid':16,'carnation':8,'rose':15}
tea={'红茶':30,'绿茶':20,'茉莉花茶':40,'红茶':13}
print("一支玫瑰的价钱是：",flower['rose'])
print("红茶一袋的价钱是：",tea['红茶'])
print("``````````````````````````````````````````````````````````")

如上所示，字典中的元素对应值被后面的值占领了。 

4.增加字典元素 

实例：

print("``````````````````````````````````````````````````````````")
flower={'rose':10,'orchid':16,'carnation':8}
tea={'红茶':30,'绿茶':20,'茉莉花茶':40}
flower['tuilp']=13
print(flower)

print("``````````````````````````````````````````````````````````")

 5.更改元素内容

实例：

print("``````````````````````````````````````````````````````````")
flower={'rose':10,'orchid':16,'carnation':8}
tea={'红茶':30,'绿茶':20,'茉莉花茶':40}
flower['rose']=13
print(flower)
print("``````````````````````````````````````````````````````````")

6.删除字典（特定元素）

删除元素实例： 

print("``````````````````````````````````````````````````````````")
flower={'rose':10,'orchid':16,'carnation':8}
tea={'红茶':30,'绿茶':20,'茉莉花茶':40}
del flower['rose']
print(flower)
print("``````````````````````````````````````````````````````````")

 删除字典实例：

print("``````````````````````````````````````````````````````````")
flower={'rose':10,'orchid':16,'carnation':8}
del flower
print(flower)
print("``````````````````````````````````````````````````````````")

7. 字典的复制

print("``````````````````````````````````````````````````````````")
flower={'rose':10,'orchid':16,'carnation':8}
copyflower=flower.copy()
print(flower)
print(copyflower)
print("``````````````````````````````````````````````````````````")

 二、遍历字典

1.遍历字典的key-value

flower={'rose':10,
'orchid':16,
'carnation':8}
for flowers,price in flower.items():
print("花名：",flowers)
print("价格：",price)
print("\n")

2.遍历字典的键(key) 

flower={'rose':10,
'orchid':16,
'carnation':8}
for flowers in flower.keys():
print("花名：",flowers)
print("\n")

没有keys()函数也行：

flower={'rose':10,
'orchid':16,
'carnation':8}
for flowers in flower:
print("花名：",flowers)

 3.遍历字典的值（value）

flower={'rose':10,
'orchid':16,
'carnation':8}
for flowers in flower.values():
print("价格：",flowers)

 4.字典里面放字典

实例：人物介绍

role={

'鲁班':{
'技能':'土木建筑',
'职业':'工匠'
},
'钟无艳':{
'技能':'出谋划策',
'职业':'中国古代四大丑女之一'
},
'蔡文姬':{
'技能':'琴棋书画',
'职业':'董祀之妻'
}

}
for a,b in role.items():
print("姓名：",a)
print("介绍：",b)

三、简单介绍下函数

len()：求元素个数

get()：搜寻字典的key

格式：返回值=字典名.get('key')

pop()：删除元素

格式：返回值=字典名.pop('key')

来源：https://blog.51cto.com/hwuu/6064023