字典是以键值对(key-value)的形式存储数据的一种数据类型，在字典中键必须是唯一的，且是不可变的数据类型（int，str，tuple，bool）
通过键来找到对应的值
有则修改，无则添加
dic = {‘name‘:‘abc‘, ‘age‘:18, ‘hobby‘:‘sleep‘}
dic[‘age‘] = 20
dic[‘school‘] = ‘lalala‘
print(dic)
{‘name‘: ‘abc‘, ‘age‘: 20, ‘hobby‘: ‘sleep‘, ‘school‘: ‘lalala‘}
有则不变，无则添加
dic = {‘name‘:‘abc‘, ‘age‘:18, ‘hobby‘:‘sleep‘}
dic.setdefault(‘age‘,20)
dic.setdefault(‘school‘,‘lalala‘)
print(dic)
{‘name‘: ‘abc‘, ‘age‘: 18, ‘hobby‘: ‘sleep‘, ‘school‘: ‘lalala‘}
根据键弹出一个值，参数如下：
pop(key,default) key:要弹出的值的键 default：如果此键不在字典里，返回的值，如果不写默认报错
dic = {‘name‘:‘abc‘, ‘age‘:18, ‘hobby‘:‘sleep‘}
a = dic.pop(‘name‘)
print(a,dic)
abc {‘age‘: 18, ‘hobby‘: ‘sleep‘}
dic = {‘name‘:‘abc‘, ‘age‘:18, ‘hobby‘:‘sleep‘}
a = dic.pop(‘school‘)
print(a,dic)
KeyError: ‘school‘
dic = {‘name‘:‘abc‘, ‘age‘:18, ‘hobby‘:‘sleep‘}
a = dic.pop(‘school‘,‘此键不在字典中！‘)
print(a)
print(dic)
此键不在字典中！
{‘name‘: ‘abc‘, ‘age‘: 18, ‘hobby‘: ‘sleep‘}
随机弹出一对键值对，返回形式为元组形式的键值对，例如：
dic = {‘name‘:‘abc‘, ‘age‘:18, ‘hobby‘:‘sleep‘}
a = dic.popitem()
print(a)
print(dic)
(‘hobby‘, ‘sleep‘)
{‘name‘: ‘abc‘, ‘age‘: 18}
清空字典
dic = {‘name‘:‘abc‘, ‘age‘:18, ‘hobby‘:‘sleep‘}
dic.clear()
print(dic)
{}
将字典在内存中删除
dic = {‘name‘:‘abc‘, ‘age‘:18, ‘hobby‘:‘sleep‘}
del dic
print(dic)
NameError: name ‘dic‘ is not defined
见 增 的 直接赋值
用一个其他字典更新原字典
dic = {‘name‘:‘abc‘, ‘age‘:18, ‘hobby‘:‘sleep‘}
dic2 = {‘school‘:‘lalala‘,‘date‘:‘aaaa‘}
dic.update(dic2)
print(dic)
{‘name‘: ‘abc‘, ‘age‘: 18, ‘hobby‘: ‘sleep‘, ‘school‘: ‘lalala‘, ‘date‘: ‘aaaa‘}
如果其他字典中有与原字典相同的键，则覆盖原字典中的值
dic = {‘name‘:‘abc‘, ‘age‘:18, ‘hobby‘:‘sleep‘}
dic2 = {‘name‘:‘AAA‘,‘school‘:‘lalala‘}
dic.update(dic2)
print(dic)
{‘name‘: ‘AAA‘, ‘age‘: 18, ‘hobby‘: ‘sleep‘, ‘school‘: ‘lalala‘}
有一个缺点，找不到会报错
dic = {‘name‘:‘abc‘, ‘age‘:18, ‘hobby‘:‘sleep‘}
print(dic[‘name‘])
abc
可自定义找不到返回的内容
参数 get(键，找不到返回的内容) 找不到返回的内容默认为None
dic = {‘name‘:‘abc‘, ‘age‘:18, ‘hobby‘:‘sleep‘}
print(dic.get(‘name‘))
print(dic.get(‘school‘))
print(dic.get(‘school‘,‘没有此键‘))
abc
None
没有此键
找到字典中所有的键，返回的数据类型为 dict_keys , 可与for搭配遍历字典的值
dic = {‘name‘:‘abc‘, ‘age‘:18, ‘hobby‘:‘sleep‘}
print(dic.keys())
dict_keys([‘name‘, ‘age‘, ‘hobby‘])
找到字典中所有的值，返回的数据类型为 dict_values ， 可与for搭配遍历字典的值
dic = {‘name‘:‘abc‘, ‘age‘:18, ‘hobby‘:‘sleep‘}
print(dic.values())
dict_values([‘abc‘, 18, ‘sleep‘])
找到字典中所有的j键值对，返回的数据类型为 dict_items ，
可与for搭配遍历字典的键值对，循环时可以用两个变量分别接收键和值
dic = {‘name‘:‘abc‘, ‘age‘:18, ‘hobby‘:‘sleep‘}
print(dic.items())
dict_items([(‘name‘, ‘abc‘), (‘age‘, 18), (‘hobby‘, ‘sleep‘)])
dic = {‘name‘:‘abc‘, ‘age‘:18, ‘hobby‘:‘sleep‘}
for i,j in dic.items() :
print(i,j)
name abc
age 18
hobby sleep
集合内的元素无序，不重复，可哈希，但集合本身是不可哈希的（不能作为字典的key）
集合主要有两大作用：
1、去重
2、数据关系测试
set1 = {‘abc‘, 18 ,‘sleep‘}
set1.add(‘lalala‘)
print(set1)
{‘abc‘, 18, ‘sleep‘, ‘lalala‘}
迭代添加，添加的内容必须是可迭代的
set1 = {‘abc‘, 18 ,‘sleep‘}
set1.update(‘def‘)
print(set1)
{‘d‘, ‘sleep‘, ‘e‘, 18, ‘f‘, ‘abc‘}
remove的元素必须是集合内有的
set1 = {‘abc‘, 18 ,‘sleep‘}
set1.remove(18)
print(set1)
{‘abc‘, ‘sleep‘}
随机弹出一个元素
set1 = {‘abc‘, 18 ,‘sleep‘}
a = set1.pop()
print(a,set1)
sleep {18, ‘abc‘}
与其他数据类型用法相同
由于集合的无序性，所以必须用for循环来遍历集合
list1 = [111,222,333,111,222,333,555,444] set1 = set(list1) print(set1) {555, 333, 111, 444, 222}
可以看到，集合和字典一样是用{}定义的，所以在定义一个空集合时，不能用{}，而用set()
a = {} b = set() print(type(a)) print(type(b)) <class ‘dict‘> <class ‘set‘>
set1 = {1,2,3,4,5}
set2 = {3,4,5,6,7}
a = set1 & set2
print(a)
{3, 4, 5}
set1 = {1,2,3,4,5}
set2 = {3,4,5,6,7}
a = set1 | set2
print(a)
{1, 2, 3, 4, 5, 6, 7}
set1 = {3,4,5}
set2 = {3,4,5,6,7}
print(set1.issubset(set2))
print(set2.issuperset(set1))
True
True
直接进行减运算
set1 = {1,2,3,4,5}
set2 = {3,4,5,6,7}
print(set1 - set2)
print(set2 - set1)
{1, 2}
{6, 7}
set1 = {1,2,3,4,5}
set2 = {3,4,5,6,7}
print(set1 ^ set2)
{1, 2, 6, 7}
原文：https://www.cnblogs.com/python-CC/p/10668409.html