dict

Posted 2021-03-12 wenshu

字典常用的方法包含：

　　1、增加key-value；通过dict_stu[key_new]={value_new}; 通过dict_stu.update(dict_new);

　　2、修改某个key对应的value；通过dict_stu[key_modify]={values_new}

　　3、查找某个key对应的value；通过dict_stu[key_find]; 通过dict_stu.get(key_find); 通过dict_stu.setdefault(key_find,"defualt value");

　　3.1、返回字典中所有的值；通过dict_stu.values()

　　4、删除某个key对应的value；通过del dict_stu[key_del]; 通过dict_stu.pop(key_del);

　　5、复制一个字典：通过dict_stu.copy()

　　6、判断字典key是否在字典中：通过key in dict_stu; 通过key not in dict_stu

　　7、计算字典的长度：通过len(dict_stu)

　　8、创建一个（不）含默认值的字典：dict.fromkeys(key_list,values)

　　9、删除整个字典：通过del dict_stu; 通过dict_stu.clear()

 

10 dict的拷贝
my_dict = {"bobby": 22, "bobby1": 33, "imooc": {"hello":11}}
a = my_dict.copy()
print(a)
a["imooc"]["hello"]=45
#浅拷贝-------没有做嵌套的拷贝
import copy
new_dict = {"bobby": 22, "bobby1": 33, "imooc": {"hello":11}}
b = copy.deepcopy(new_dict)
b["imooc"]["hello"] = 99
pass
#深拷贝-----完全将数据做了一个嵌套的拷贝

 

 

 

 

例如：
#返回字典的成员个数;return the number of items in the dictionary
print("after add item.the length of dict is:",len(dict_stu))

#删除字典某个key的成员，如果没有key抛出异常;remove dict_stu[key] from dict,Raises a KeyError if key is not in the map
del dict_stu["171003"]

#返回并删除字典中某个key的值或default，如果key存在返回key对应的值，如果key不存在，设置了default则返回defalut值，如果没设置则报错
print("33[31;1mtest the pop method:33[0m",dict_stu.pop("171002"))
#pop方法没有设置default，测试报错
#print("33[31;1mtest the pop method,there is no 171002 key33[0m",dict_stu.pop("171002"))
#pop方法有设置default，测试正常
print("33[31;1mtest the pop method,there is no 171002 key:33[0m",dict_stu.pop("171002","the default is defined"))

#return the number of items in the dictionary
print("after del item.the length of dict is:",len(dict_stu))

#测试key是否在字典中,如果存在返回true ,同key not in d;retrun True if dict_stu has a key ‘key‘ ,else False
print("33[31;1mtest the 171003 is the dict_stu‘s key?33[0m","171003" in dict_stu)

#返回字典中key对应的value,如何没有返回None;retrun the value for key if key is in the dictionary,else default return None
print("return the 171001‘s values:",dict_stu.get("171001"))

#如果key在字典中,返回字典中key对应的value;如果key没有在字典中,返回默认值
print("33[31;1msetdefault methord return the 171001‘s values:33[0m",dict_stu.setdefault("171001","default values"))
print("33[41;1msetdefault methord return the 171008‘s values:33[0m",dict_stu.setdefault("171008","default values"))

#方法1:升级一个字典;update the dictionary
dict_stu.update(new_stu)
print("33[21;1muse update method update the dict_stu:33[0m",dict_stu)

#字典的浅复制
dict_copy = dict_stu.copy();
print("33[41;1mthe copy of the dict_stu33[0m",dict_copy)
print("test the copy dict is equle the org dict:",dict_copy == dict_stu)
print("the dict of dict_stu",dict_stu)

#return a new view of the dictionary‘s values
print(" the dict_stu.values methord: ",dict_stu.values())

#创建一个字典通过fromkeys方法,以序列seq中元素做字典的键，value为字典所有键对应的初始值
dict1_fromkeys = dict.fromkeys([1,2,3,4],50)
dict2_fromkeys = dict.fromkeys([1,2,3,4],[50,20,10,79])
dict3_fromkeys = dict.fromkeys([1,2,3,4],set([50,20,10,79]))
print("33[31;1mcreate a dict with keys from seq and values set33[0m",dict1_fromkeys)
print("33[31;1mcreate a dict with keys from seq and values set33[0m",dict2_fromkeys)
print("33[31;1mcreate a dict with keys from seq and values set33[0m",dict3_fromkeys)
dict1_fromkeys[1]="修改"
#由于是浅复制，所以修改列表中的一个元组，其它节点就都修改了
dict2_fromkeys[1][0]="90"
print("33[31;1mmodify the dict with keys from seq and values set33[0m",dict1_fromkeys)
print("33[31;1mmodify the dict with keys from seq and values set33[0m",dict2_fromkeys)

#返回字典中所有的值
print("return a new view of the dictionary‘s values:",dict_stu.values())
#remove all items from the dictionary
dict_stu.clear()
print("after clear the dict is:",dict_stu)