dict的增，删，改，查

Posted 2020-10-12

 dict是无序的 ，数据关联性强，键值对，唯一一个个映射的数据类型
  字典的键必须是可哈希的数据类型 （字符串，数字，bool，元祖）并且是唯一的.
  不可哈希的:（列表，字典）

dict的增

1:直接加键值对，如果和要增的相同就会覆盖，没有才添加

dic = {‘name‘:‘wujiang‘,‘age‘:18,}
dic[‘hobby‘] = ‘it‘
print(dic)   #：{‘name‘: ‘wujiang‘, ‘age‘: 18, ‘hobby‘: ‘it‘} 

2.setdefault（）有的键值对不变，没有的添加

dic = {‘name‘:‘wujiang‘,‘age‘:18,}
dic.setdefault(‘k1‘,‘v‘)
print(dic)   #{‘name‘: ‘wujiang‘, ‘age‘: 18, ‘k1‘: ‘v‘}

dict的删

1.pop按照键去删，有返回值

dic = {‘name‘:‘wujiang‘,‘age‘:18,}
dic.pop(‘name‘)
print(dic)  #：{‘age‘: 18}

2.del 直接删键

dic = {‘name‘:‘wujiang‘,‘age‘:18,}
del dic[‘age‘]  #注意格式
print(dic) #：{‘name‘: ‘wujiang‘}

3.clear 清空列表

dic = {‘name‘:‘wujiang‘,‘age‘:18,}
dic.clear()
print(dic)  #{}

dict的改：

1.直接改键

dic = {‘name‘:‘wujiang‘,‘age‘:18,}
dic[‘name‘] = ‘taibai‘
print(dic)  #：{‘name‘: ‘taibai‘, ‘age‘: 18}

2.update 更新原dic（就是添加并覆盖）

dic = {‘name‘:‘wujiang‘,‘age‘:18,‘hobby‘:‘lol‘}
dic.update( {‘name‘:‘taibai‘})
print(dic)     #：{‘name‘: ‘taibai‘, ‘age‘: 18, ‘hobby‘: ‘lol‘}
                  # ：只变原字典        

dict的查

1.直接查键

dic = {‘name‘:‘wujiang‘,‘age‘:18,‘hobby‘:‘lol‘}
dic1 = dic[‘hobby‘]
print(dic1)    #：lol

2.get  查键，没有返回None

dic = {‘name‘:‘wujiang‘,‘age‘:18,‘hobby‘:‘lol‘}
dic1 = (dic.get(‘jop‘))
print(dic1)   #：None

dic的特殊类型：keys(键),values（值）,items（键值对）,

dic = {‘name‘:‘wujiang‘,‘age‘:18,‘hobby‘:‘lol‘}
dic1 = dic.keys()
print(dic1)  #：dict_keys([‘name‘, ‘age‘, ‘hobby‘])

dic = {‘name‘:‘wujiang‘,‘age‘:18,‘hobby‘:‘lol‘}
dic1 = dic.values()
print(dic1) #：dict_values([‘wujiang‘, 18, ‘lol‘])

dic = {‘name‘:‘wujiang‘,‘age‘:18,‘hobby‘:‘lol‘}
dic1 = dic.items()
print(dic1)
 #：dict_items([(‘name‘, ‘wujiang‘), (‘age‘, 18), (‘hobby‘, ‘lol‘)])