python中的字典

红太狼 2021-12-14 11:35 358阅读 0赞

## 1.字典的定义 ##

字典是一个无序的数据集合  
通常输出的顺序和定义的顺序不一致

**1.列表类型转换**

users = ['user1','user2']
    passwd = ['123','456']
    print(zip(users,passwd))	##无法正确输出
    print(list(zip(users,passwd)))	##将类型转换成列表类型输出
    print(dict(zip(users,passwd)))	##将类型转换成字典类型输出

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70]**2.空字典**

s = {}
    print(type(s))

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 1]  
**3.创建字典并输出其类型**  
\#\#字典：key-value键值对  
\#value可以是任意数据类型

s = {
        'westos':[190,521,231],
        'mysql':[100,99,88]
    }
    
    print(s,type(s))

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 2]  
**4.工厂函数**

#工厂函数
    d = dict()	##dict相当于一个函数
    print(type(d))	##查看d是一个类型
    #举例
    d1 = dict(a=1,b=2)
    print(d1,type(d1))

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 3]  
**5.字典的嵌套**

students = {
        '03113009':{
            'name':'szy',
            'age':21,
            'score':99
        },
        '03113010':{
            'name':'westos',
            'age':18,
            'score':61
        }
    }
    print(students['03113009']['name'])

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 4]**6.所有的key对应的value值是一样的**

print({}.fromkeys({'1','2'},'000000'))

![在这里插入图片描述][20190704220241601.png]

## 2.字典的特性 ##

**字典不支持索引和切片，且字典的重复和连接毫无意义**

d = {
        '1':'a',
        '2':'b'
    }
    print(d['1'])
    print(d[:])

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 5]**成员操作符**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 6]  
**for循环，默认变量字典的key值**

d = {
        '1':'a',
        '2':'b'
    }
    for key in d:
        print(key)

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 7]

**for循环，遍历字典（输出key值和value值）**

d = {
        '1':'a',
        '2':'b'
    }
    for key in d:
        print(key,d[key])
    
    d = {
        '1':'a',
        '2':'b'
    }
    for k,v in d.items():
        print(k,v)

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 8]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 9]

## 3.字典的增加 ##

**1.添加一个元素**

services = {
        'http':80,
        'mysql':3306,
        'smtp':25
    }
    
    services['ftp'] = 21
    print(services)
    
    services['http'] = 443
    print(services)

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 10]  
**2.添加多个key-value值**

services = {
        'http':80,
        'mysql':3306,
        'smtp':25
    }
    services_backup = {
        'https':443,
        'tomcat':8080,
        'http':8080
    }
    
    services.update(services_backup)
    print(services)

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 11]  
**3.setdefault添加key值**  
\#如果key值存在，不做修改  
\#如果key值不存在，添加对应的key-value

services = {
        'http':80,
        'mysql':3306,
        'smtp':25
    }
    services.setdefault('http',9090)
    print(services)
    
    services.setdefault('oracle',44575)
    print(services)

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 12]

## 4.字典的删除 ##

**1.del删除指定的key的key-value**

services = {
        'http':80,
        'mysql':3306,
        'smtp':25
    }
    del services['http']
    print(services)

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 13]  
**2.pop删除指定的key的key-value**  
\#如果key存在，删除，并返回删除key对应value  
\#如果不存在，报错

services = {                      
        'http':80,                    
        'mysql':3306,                 
        'smtp':25                     
    }                                 
    item = services.pop('http')       
    print(item)                       
    print(services)                   
    item1 = services.pop('https')     
    print(item1)                      
    print(services)

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 14]  
**3.popitem删除最后一个key-value值**

services = {                 
        'http':80,               
        'mysql':3306,            
        'smtp':25                
    }                            
    item = services.popitem()    
    print(services)

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 15]**4.清空字典内容**

services = {       
        'http':80,     
        'mysql':3306,  
        'smtp':25      
    }                  
    services.clear()   
    print(services)

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 16]

## 5.字典的查看 ##

**1.查看字典的key值**

services = {
        'http':80,
        'mysql':3306,
        'smtp':25
    }
    print(services.keys())

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 17]**2.查看字典的value值**

services = {
        'http':80,
        'mysql':3306,
        'smtp':25
    }
    
    print(services.values())

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 18]  
**3.查看字典的key-value值**

services = {
        'http':80,
        'mysql':3306,
        'smtp':25
    }
    
    print(services.items())

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 19]**4.查看key的value值**  
\#key不存在，默认返回None  
\#key不存在，有default，则返回default值

services = {
        'http':80,
        'mysql':3306,
        'smtp':25
    }
    
    print(services.get('https'))
    print(services.get('http'))

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 20]  
get方法  
如果key值存在，返回  
如果不存在，默认返回None，如果需要指定返回值，传值即可

services = {
        'http':80,
        'mysql':3306,
        'smtp':25
    }
    
    print(services.get('https','key not exist'))

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 21]

**5.遍历**

services = {
        'http':80,
        'mysql':3306,
        'smtp':25
    }
    
    for k in services:
        print(k,services[k])

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 22]

## 6.字典的练习 ##

1. 数字重复统计:  
要求：  
1). 随机生成1000个整数;  
2). 数字的范围\[20, 100\],  
3). 升序输出所有不同的数字及其每个数字重复的次数;

all_num = []
    for item in range(1000):
        all_num.append(random.randint(20,100))
    
    print(all_num)
    sorted_nums = sorted(all_num)
    num_dict = {}
    
    for num in sorted_nums:
        if num in num_dict:
            num_dict[num] += 1
        else:
            num_dict[num] = 1
    
    print(num_dict)

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 23]2.统计一句话中的单词出现的个数  
要求：

1.  用户输入一句英文句子；
2.  打印出每个单词及其重复的次数;

s = input('s:')
    #1.把每个单词分割处理
    s_li = s.split()
    print(s_li)
    #通过字典存储该单词和其出现的次数
    word_dict = {}
    """
    依次循环遍历列表
        如果列表元素不在字典的key中，将元素作为key 1作为value值
        如果列表元素在字典的key中，直接更新元素的value值，在原有的基础上加1
    """
    for item in s_li:
        if item not in word_dict:
            word_dict[item] = 1
        else:
            word_dict[item] += 1
    print(word_dict)

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDg4OTYxNg_size_16_color_FFFFFF_t_70 24]

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[20190704220241601.png]: /images/20211214/ddb4664bfe704ea6803a1de3e2f2ac13.png
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