day06_06 字典操作01

1.0 字典操作

dic1 = {‘name‘:‘alex‘}
dic1[‘age‘] = 18
print(dic1)
#>>>{‘age‘: 18, ‘name‘: ‘alex‘}

1.1 字典修改键

dic1 = {‘name‘:‘alex‘}
dic1[‘name‘] = ‘wang‘
print(dic1)
#>>>{‘name‘: ‘wang‘}

1.2 setdefault用法,添加键值(如果之前已经有相同键了,那么就不做修改),有返回值

dic1 = {‘name‘:‘alex‘,‘age‘:18}
dic1.setdefault(‘age‘,34)
print(dic1)
#>>>{‘age‘: 18, ‘name‘: ‘alex‘}

dic1 = {‘name‘:‘alex‘}
dic1.setdefault(‘age‘,34)
print(dic1)
#>>>{‘name‘: ‘alex‘, ‘age‘: 34}

1.3 setdefault返回值测试

dic1 = {‘name‘:‘alex‘}
dic1[‘age‘] = 18
print(dic1)
#>>>{‘name‘: ‘alex‘, ‘age‘: 18}
#键存在的话,不改动,返回字典中相应的键对应的值
ret = dic1.setdefault(‘age‘,34)
print(ret)
#>>>18
#键不存在,在字典中增加新的键值对,并返回相应的值
ret2 = dic1.setdefault(‘hobby‘,‘girl‘)
print(ret2)
#>>>girl

1.4 查找

#查 通过键去查找
dic3 = {‘age‘:18,‘name‘:‘alex‘,‘hobby‘:‘girl‘}
print(dic3[‘name‘])
#>>>alex
print(dic3.keys())
#>>>dict_keys([‘name‘, ‘age‘, ‘hobby‘])

#查 通过键去查找
dic3 = {‘age‘:18,‘name‘:‘alex‘,‘hobby‘:‘girl‘}
print(dic3[‘name‘])
#>>>alex
print(dic3.keys())
#>>>dict_keys([‘name‘, ‘age‘, ‘hobby‘])
print(type(dic3.keys())) #查看类型,是个dict_keys的类
#>>><class ‘dict_keys‘>
print(list(dic3.keys())) #键转换成列表
#>>>[‘name‘, ‘age‘, ‘hobby‘]
print(type(dic3.values()))
#>>><class ‘dict_values‘>
print(list(dic3.values())) #值转换成列表
#>>>[‘alex‘, 18, ‘girl‘]
print(list(dic3.items()))
#>>>[(‘name‘, ‘alex‘), (‘hobby‘, ‘girl‘), (‘age‘, 18)]

1.5 改

li = [1,2,3,4]
li[2] = 5
dic3 = {‘age‘:18,‘name‘:‘alex‘,‘hobby‘:‘girl‘}
dic3[‘age‘] = 55
print(dic3)
#>>>{‘hobby‘: ‘girl‘, ‘age‘: 55, ‘name‘: ‘alex‘}

1.6 update方法

dic4 = {‘age‘:18,‘name‘:‘alex‘,‘hobby‘:‘girl‘}
dic5 = {‘1‘:‘111‘,‘2‘:‘222‘}
dic4.update(dic5)
print(dic4)
#>>>{‘hobby‘: ‘girl‘, ‘age‘: 18, ‘2‘: ‘222‘, ‘name‘: ‘alex‘, ‘1‘: ‘111‘}
print(dic5)
#>>>{‘1‘: ‘111‘, ‘2‘: ‘222‘}

dic4 = {‘age‘:18,‘name‘:‘alex‘,‘hobby‘:‘girl‘}dic6 = {‘name‘:‘wangba‘}dic4.update(dic6)print(dic4)#>>>{‘hobby‘: ‘girl‘, ‘name‘: ‘wangba‘, ‘age‘: 18}