字典总结

字典总结

字典概念

字典是“键名-数值对”的无序集合，键是唯一的、不可变的，值是可变的。

字典初始化

my_dict = {"Wang":1998,"Liu":1998,"Guo":1997}
my_dict["Wang"]

1998

my_dict = {"Wang":1998,"Liu":1998,"Guo":1997}
my_dict['Wang'] = 1996
my_dict

{'Wang': 1996, 'Liu': 1998, 'Guo': 1997}

my_dict = {"Wang":1998,"Liu":1998,"Guo":1997}
my_dict["Tan"] = 1999
my_dict

{'Wang': 1998, 'Liu': 1998, 'Guo': 1997, 'Tan': 1999}

my_dict.get('Wang',None)#同上面取值一样但是如果没有匹配到相应的键返回None

1998

my_dict = {"Wang":1998,"Liu":1998,"Guo":1997}
my_dict.items()#返回一个列表列表的每个元素为一个二位元组

dict_items([('Wang', 1998), ('Liu', 1998), ('Guo', 1997)])

my_dict = {"Wang":1998,"Liu":1998,"Guo":1997}
"hui" in my_dict#判断某个键是否在字典中

False

my_dict = {"Wang":1998,"Liu":1998,"Guo":1997}
del my_dict["Liu"]#删除对应的键与值
my_dict

{'Wang': 1998, 'Guo': 1997}

历遍字典所有的键与值

my_dict = {"Wang":1998,"Liu":1998,"Guo":1997}
for i in my_dict.items():
    print(i)

('Wang', 1998)
('Liu', 1998)
('Guo', 1997)

单独历遍键与值

my_dict = {"Wang":1998,"Liu":1998,"Guo":1997}
for i in my_dict.keys():
    print(i)
for j in my_dict.values():
    print(j)

Wang
Liu
Guo
1998
1998
1997

删除并将删除的键的值赋值给其他变量使用pop同字符串与列表

my_dict = {"Wang":1998,"Liu":1998,"Guo":1997}
a = my_dict.pop("Wang")
print (a)
my_dict

1998





{'Liu': 1998, 'Guo': 1997}

my_dict = {"Wang":1998,"Liu":1998,"Guo":1997}
a = my_dict.popitem()#popitem返回一个二元元组
a

('Guo', 1997)

清除所有的键对

my_dict = {"Wang":1998,"Liu":1998,"Guo":1997}
my_dict.clear()
my_dict

{}

添加键对

my_dict = {"Wang":1998,"Liu":1998,"Guo":1997}
dict_a = {"hui":888}
dict_b = {"pu":250}
my_dict.update(dict_a, **dict_b)
my_dict

{'Wang': 1998, 'Liu': 1998, 'Guo': 1997, 'hui': 888, 'pu': 250}