python学习：字典

Posted 2020-12-30 pl-2018

字典

1.查询内存地址

a = 10

print(id(a))

b = a

print(id(b))

b = 15

print(id(b))

2. 数据类型

不可变类型：整型、字符串、元组

可变类型：列表、字典

字典的值可以是任意类型，键只能是不可变类型。

字典存储是无序的。例如：

dic = {‘name‘:‘ysw‘,‘age‘:36,‘hobby‘:‘game‘,‘is_handsome‘:True}

print(dic)

print(dic[‘name‘])

#dic = {1:‘ysw‘,‘age‘:36,‘hobby‘:‘game‘,‘is_handsome‘:True}

#print(dic)

#print(dic[1])

#dic = {[1,2]:‘ysw‘,‘age‘:36,‘hobby‘:‘game‘,‘is_handsome‘:True}

#print(dic)

#print(dic[[1,2]])

#dic = {‘name‘:‘ysw‘,‘age‘:36,‘hobby‘:{‘game_name‘:‘wow‘,‘level‘:‘20‘},‘is_handsome‘:True}

#print(dic[‘hobby‘])

#dic = {{‘1‘:‘123‘},‘age‘:36,‘hobby‘:{‘game_name‘:‘wow‘,‘level‘:‘20‘},‘is_handsome‘:True}

#print(dic)

#字典两大特点：无序；键唯一

#dic = {‘age‘:‘ysw‘,‘age‘:36,‘hobby‘:‘game‘,‘is_handsome‘:True}

#print(dic)

3.字典的两种创建方式：

#dic1 = {‘name‘:‘ysw‘}

#dic2 = dict(((‘name‘,‘ysw‘),))

 4.对应操作

　　（1）增

dic1 = {‘name‘:‘ysw‘}

dic1[‘age‘] = 18

print(dic1)

dic1[‘name‘] = 18

print(dic1)

#没有重复的键就添加，有重复的键就替换数值

------------------------------

dic1 = {‘name‘:‘ysw‘}

dic1[‘age‘] = 18

print(dic1)

dic1.setdefault(‘age‘,36)

print(dic1)

#dic1.setdefault(‘hobby‘,‘game‘)

#print(dic1)

#setdefault的特点：没有重复的键就添加，有重复的键就没有变化