age=dic1.setdefault('age',18)
print(age)

键存在，不改动，返回字典中相应的键对应的值,输出为20

hobby=dic1.setdefault('hobby','sport')
print(hobby)

键不存在，在字典中中增加新的键值对，并返回相应的值，输出为sport

print(dic3['name'])#输出a
print(dic3.get("name"))#输出aprint(dic3.get("sex","male"))#如果有sex键则返回对应的值，没有的话返回"male"
print(dic3.keys())#输出dict_keys(['age','name','hobby']),其他同理
print(list(dic3.keys()))#输出['age','hobby']
print(list(dic3.values()))#输出[20,'a','sport']
print(list(dic3.items()))#输出[('age',20),('name',('hobby','sport')]

更新字典

dic4={'age': 20,'hobby':'sport'}
dic5={'1':'111','name':'222'}
dic4.update(dic5)
print(dic4)#输出{'age': 20,'name': '222','hobby': 'sport','1': '111'}
print(dic5)#输出{'1': '111','name': '222'}

dic5.clear() # 清空字典

del dic5['name'] #删除字典中指定键值对

print(dic5.pop('age')) #删除字典中指定键值对，并返回该键值对的值，应该输出20

a = dic5.popitem() #随机删除某组键值对，并以元组方式返回值

del dic5 #删除整个字典

dic6=dict.fromkeys(['host1',['test1','tets2'])
print(dic6)#{'host2': ['test1','tets2'],'host3': ['test1','host1': ['test1','tets2']}

dic6['host2'][1]='test3'
print(dic6)

{'host3': ['test1','test3'],'host2': ['test1','test3']}，这里不仅仅只改变了host2的值

for i in dic5:
print(i,dic5[i])

for i,v in dic5.items():
print(i,v)