字典的一些操作

Posted 2020-12-25 albatorss

字典

字典是python中唯一的映射类型，采用键值对（key-value）的形式存储数据。python对key进行哈希函数运算，根据计算的结果决定value的存储地址，所以字典是无序存储的，且key必须是可哈希的。可哈希表示key必须是不可变类型，如：数字、字符串、元组。

1.增

加入列表

dic = {‘name‘: ‘Alisita‘, ‘age‘: ‘45‘, ‘hobbie‘: ‘run‘}
dic[‘li‘] = [‘a‘]
print(dic)

#输出
    {‘name‘: ‘Alisita‘, ‘age‘: ‘45‘, ‘hobbie‘: ‘run‘, ‘li‘: [‘a‘]}

无则添加

dic = {‘name‘: ‘Alisita‘, ‘age‘: ‘45‘, ‘hobbie‘: ‘run‘}
dic[‘high‘]=185
print(dic)

#输出
    {‘name‘: ‘Alisita‘, ‘age‘: ‘45‘, ‘hobbie‘: ‘run‘, ‘high‘: 185}

有则覆盖

dic = {‘name‘: ‘Alisita‘, ‘age‘: ‘45‘, ‘hobbie‘: ‘run‘}
dic[‘name‘]=‘Delaiesi‘
print(dic)

#输出
    {‘name‘: ‘Delaiesi‘, ‘age‘: ‘45‘, ‘hobbie‘: ‘run‘}

setdefault

有键值对不作任何改变，没有才添加

dic = {‘name‘: ‘Alisita‘, ‘age‘: ‘45‘, ‘hobbie‘: ‘run‘}
dic.setdefault(‘weight‘，180)
print(dic)

#输出
    {‘name‘: ‘Alisita‘, ‘age‘: ‘45‘, ‘hobbie‘: ‘run‘, ‘weight‘: 180}

 

2.删

pop     pop根据key删除键值对，并返回对应的值，如果没有key则返回默认返回值

dic = {‘name‘: ‘Alisita‘, ‘age‘: ‘45‘, ‘hobbie‘: ‘run‘}
dic_pop=dic.pop(‘name‘)
print(dic_pop)
print(dic)

#输出
    Alisita
{‘age‘: ‘45‘, ‘hobbie‘: ‘run‘}

popitem     随机删除字典中的某个键值对，将删除的键值对以元祖的形式返回

dic = {‘name‘: ‘Alisita‘, ‘age‘: ‘45‘, ‘hobbie‘: ‘run‘}
dic_pop=dic.popitem()
print(dic_pop)
print(dic)

#输出
    (‘hobbie‘, ‘run‘)
{‘name‘: ‘Alisita‘, ‘age‘: ‘45‘}

clear   清空字典中的元素

dic = {‘name‘: ‘Alisita‘, ‘age‘: ‘45‘, ‘hobbie‘: ‘run‘}
dic.clear()
print(dic)

#输出
    {}

 

3.改

将dic所有的键值对覆盖添加（相同的覆盖，没有的添加）到dic1中

dic = {‘name‘: ‘Alisita‘, ‘age‘: ‘45‘, ‘hobbie‘: ‘run‘}
dic1 = {‘name‘: ‘Aoraf‘, ‘sex‘: ‘male‘}
dic1.update(dic)
print(dic)
print(dic1)

#输出
    {‘name‘: ‘Alisita‘, ‘age‘: ‘45‘, ‘hobbie‘: ‘run‘}
    {‘name‘: ‘Alisita‘, ‘sex‘: ‘male‘, ‘age‘: ‘45‘, ‘hobbie‘: ‘run‘}

 

4.查

dic = {‘name‘: ‘Alisita‘, ‘age‘: ‘45‘, ‘hobbie‘: ‘run‘}
name = dic[‘name‘]
print(name)

#输出
    Alisita

get       dic.get(‘要查找的元素‘，设定的返回值)  #如果字典中没有要找的项，则返回设定的返回值，若果没有设定返回值，则返回，默认返回值

dic = {‘name‘: ‘Alisita‘, ‘age‘: ‘45‘, ‘hobbie‘: ‘run‘}
name = dic.get(‘sex‘,0)
print(name)

#输出
    0

dic = {‘name‘: ‘Alisita‘, ‘age‘: ‘45‘, ‘hobbie‘: ‘run‘}
name = dic.get(‘name‘,0)
print(name)

#输出
    Alisita

 

 

5.其他操作

dic = {‘name‘: ‘Alisita‘, ‘age‘: ‘45‘, ‘hobbie‘: ‘run‘}
for item in dic.items():
    print(item)

#items : ‘name‘: ‘Alisita‘
#keys :‘name‘
#values :‘Alisita‘

 

字典的循环

dic = {‘name‘: ‘Alisita‘, ‘age‘: ‘45‘, ‘hobbie‘: ‘run‘}
for key in dic:
    print(key)

#输出
    name
    age
    hobbie


dic = {‘name‘: ‘Alisita‘, ‘age‘: ‘45‘, ‘hobbie‘: ‘run‘}
for item in dic.items():
    print(item)

#输出
    (‘name‘, ‘Alisita‘)
    (‘age‘, ‘45‘)
    (‘hobbie‘, ‘run‘)


dic = {‘name‘: ‘Alisita‘, ‘age‘: ‘45‘, ‘hobbie‘: ‘run‘}
for key,value in dic.items():
    print(key,value)

#输出
    name Alisita
    age 45
    hobbie run