字典fromkeys方法和update方法

 #Author : Kelvin
 #Date : 2019/1/17 15:27

 #字典的update方法，是向调用者字典中添加另外一个字典
 dict1 = {"name":"kelvin", "age": 22}
 dict2 = {"sex":"male"}
 dict1.update(dict2)
 print(dict1)
 #>>>: {'name': 'kelvin', 'age': 22, 'sex': 'male'}

 #字典的fromkeys方法
 list1=["kelvin","bob","jam"]
 new_dict1=dict.fromkeys(list1,"good")
 print(new_dict1)
 #>>>: {'kelvin': 'good', 'bob': 'good', 'jam': 'good'}
 new_dict2=dict.fromkeys(list1)
 print(new_dict2)
 #>>>: {{'kelvin': None, 'bob': None, 'jam': None}