dic = {1:2,3:4,5:6}
dic['呦'] = '爱你'
print(dic)
>>>{1: 2, 3: 4, 5: 6, '呦': '爱你'}

dic = {1:2,3:4,5:6}
dic.setdefault(7,8)
print(dic)
>>>{1: 2, 3: 4, 5: 6, 7: 8}#若是有这个键

dic = {1:2,3:4,5:6}
dic.setdefault(5,8)
print(dic)
>>>{1: 2, 3: 4, 5: 6}

dic ={1: 2, 3: 4, 5: 6}
dic.pop(3)
print(dic)
>>>{1: 2, 5: 6}

dic ={1: 2, 3: 4, 5: 6}
print(dic.popitem())
print(dic)
>>>(5,6)
>>>{1: 2, 3:4}

dic = {1:2,3:4,5:6}
dic[3] = '1+2'
print(dic)
>>>{1: 2, 3: '1+2', 5: 6}

dic = {'a':1,'b':2,'c':3}
dic.update({'c':'1+2','d':4})
print(dic)
>>>{'a': 1, 'b': 2, 'c': '1+2', 'd': 4}#括号内放的是字典,所以我们可以理解为使用后面那个字典去更新前面这个字典
dic = {'a':1,'b':2,'c':3}
dict = {'c':'1+2','d':4}
dic.update(dict)
print(dic)
>>>{'a': 1, 'b': 2, 'c': '1+2', 'd': 4}#那么这种写法也是可以的

dic = {'a':1,'b':2,'c':3}
s = dic.get('a')
print(s)
>>>1
#若是填写的键是字典中没有的,就会返回None,可以自定义返回值
dic = {'a':1,'b':2,'c':3}
s = dic.get('d')
print(s)
s2 = dic.get('d','找不到')
print(s2)
>>>None
>>>'找不到'

dic = {'a':1,'b':2,'c':3}
print(dic.keys)
>>>dict_keys(['a', 'b', 'c'])

dic = {'a':1,'b':2,'c':3}
print(dic.values())
>>>dict_values([1, 2, 3])

dic = {'a':1,'b':2,'c':3}
print(dic.items())
>>>dict_items([('a', 1), ('b', 2), ('c', 3)])

dic = {'a':1,'b':2,'c':3}
#提取键
for i in dic:print(i)
#提取值
for i in dic:print(dic[i])
#提取键值对
for i in dic:print(i,dic[i]

dic = {'a':1,'b':2,'c':3}
s = {1,2,3,4,5}
dic[frozenset(s)] = 666
print(dic)
>>>{'a': 1, 'b': 2, 'c': 3, frozenset({1, 2, 3, 4, 5}): 666}
#这个方法意义何在,,

dic = {}
dic = dic.fromkeys(['a','b','c'], [1,2])
# 第一个是键, 第二个是值
print(dic)
dic["a"].append(3) # 所有的值都会添加,只有列表会全添加,因为列表是可变的
print(dic)