字典类型

Posted 2021-01-21 kp1995

字典是另一种可变容器模型,且可存储任意类型对象.字典的每个键值对(key=>value)分隔.

用途:记录多个值,列表是索引对应值,而字典是key对应值,期中key对value有描述性功能.

d = {key1 : value1, key2 : value2}

 

类转换:

items=[(‘name‘,‘egon‘),(‘age‘,18),(‘gender‘,‘male‘)]
d={}
for item in items:
    d[item[0]]=item[1]

d=dict(items)
print(d)

#输出结果
{‘name‘: ‘egon‘, ‘age‘: 18, ‘gender‘: ‘male‘}

 

常用操作+内置方法

1.按key存取值:可存可取

dic={‘name‘:‘egon‘,‘age‘:18}
print(dic[‘name‘])
dic[‘name‘]=‘EGON‘
dic[‘gender‘]=‘male‘
print(dic)

#输出结果
egon
{‘name‘: ‘EGON‘, ‘age‘: 18, ‘gender‘: ‘male‘}

2.长度len (按key的个数取值)

dic={‘name‘:‘egon‘,‘age‘:18}
print(dic)
print(len(dic))

#输出结果
{‘name‘: ‘egon‘, ‘age‘: 18}
2

3.成员运算in和not in  :是以字典的key为准

dic={‘name‘:‘egon‘,‘age‘:18}
print(‘name‘ in dic)
print(‘egon‘ in dic)

#输出结果
True
False

4.删除

dic={‘name‘:‘egon‘,‘age‘:18}
del dic[‘name‘]
print(dic)

#输出结果
{‘age‘: 18}

dic={‘name‘:‘egon‘,‘age‘:18}
res=dic.pop(‘name‘)
print(dic)
print(res)

#输出结果
{‘age‘: 18}
egon         #有返回值

res=dic.popitem()
print(res)

#输出结果
(‘age‘, 18)

5.键keys(), 值values() , 键值对items()

>>> dic={‘name‘:‘egon‘,‘age‘:18}
>>>
>>> dic.keys()
dict_keys([‘name‘, ‘age‘])
>>> dic.values()
dict_values([‘egon‘, 18])
>>> dic.items()
dict_items([(‘name‘, ‘egon‘), (‘age‘, 18)])

6.循环

dic={‘name‘:‘egon‘,‘age‘:18}
for k in dic:
    print(k)

for k in dic.keys():
    print(k)

for v in dic.values():
    print(v)

for k,v in dic.items(): #k,v=(‘name‘, ‘egon‘)
    print(k,v)

#输出结果
name
age
name
age
egon
18
name egon
age 18