Python字典dict的常用方法和函数

Posted 2020-12-20

dict={‘name‘:‘Joe‘,‘age‘:18,‘height‘:60}

1. clear，清空

   dict.clear()
   #运行结果{}

2. pop，移除指定key的键值对并返回vlaue（如果没有该key，可返回指定值），popitem，默认移除最后一个键值对

   print(dict.pop(‘age‘))
   print(dict)
   #结果18，{‘name‘: ‘Joe‘, ‘height‘: 60}
   print(dict.pop(‘agea‘,‘erro‘))
   print(dict)
   #结果erro，{‘name‘: ‘Joe‘, ‘age‘: 18, ‘height‘: 60}
   print(dict.popitem())
   print(dict)
   #结果(‘height‘, 60)，{‘name‘: ‘Joe‘, ‘age‘: 18}

3. del，删除字典的另一种方式

   del dict[‘age‘]
   print(dict)
   #结果{‘name‘: ‘Joe‘, ‘height‘: 60}

4. get，返回指定键的值，如果值不在字典中返回default值，等同于dict.__getitem__(‘name‘)

   print(dict.get(‘name‘))
   #结果Joe
   print(dict.get(‘hobby‘))
   #结果None
   print(dict.get(‘hobby‘,‘basketball‘))
   #结果basketball

5. setdefault，和get()类似, 但如果键不存在于字典中，将会添加键并将值设为default

   print(dict.setdefault(‘hobby‘))
   print(dict)
   #结果None，{‘name‘: ‘Joe‘, ‘age‘: 18, ‘height‘: 60, ‘hobby‘: None}
   print(dict.setdefault(‘hobby‘,‘basketball‘))
   print(dict)
   #结果basketball，{‘name‘: ‘Joe‘, ‘age‘: 18, ‘height‘: 60, ‘hobby‘: ‘basketball‘}

6. update，更新字典，有key则更新该key对应的vlaue，没有则新增

   dict.update({‘age‘:20})
   print(dict)
   #结果{‘name‘: ‘Joe‘, ‘age‘: 20, ‘height‘: 60}
   dict.update({‘hobby‘:‘run‘})
   print(dict)
   #结果{‘name‘: ‘Joe‘, ‘age‘: 18, ‘height‘: 60, ‘hobby‘: ‘run‘}

7. fromkeys，创建新字典，以seq为key，vlaue为字典的初始值

   seq = (‘a‘, ‘b‘, ‘c‘)
   print(dict.fromkeys(seq))
   #结果{‘a‘: None, ‘b‘: None, ‘c‘: None}
   print(dict.fromkeys(seq,‘oh‘))
   #结果{‘a‘: ‘oh‘, ‘b‘: ‘oh‘, ‘c‘: ‘oh‘}

8. 字典的打印，取值等

   print(dict.items())
   print(dict.values())
   print(dict.keys())
   #结果
   dict_items([(‘name‘, ‘Joe‘), (‘age‘, 18), (‘height‘, 60)])
   dict_values([‘Joe‘, 18, 60])
   dict_keys([‘name‘, ‘age‘, ‘height‘])

9. 字典的遍历，遍历key

   for i in dict:
   print(i)
   #结果
   name
   age
   height
   #相同效果的遍历如下：
   for key in dict.keys():
   print(key)
   #

10. 字典的遍历，遍历值

    for vlaue in dict.values():
    print(vlaue)
    #结果
    Joe
    18
    60

11. 字典的遍历，遍历item

    #10.1输出为元组的方式
    for item in dict.items():
    print(item)
    #结果
    (‘name‘, ‘Joe‘)
    (‘age‘, 18)
    (‘height‘, 60)
    #10.2输出为字符串的方式
    for key,vlaue in dict.items():
    print(key,vlaue)
    #结果
    name Joe
    age 18
    height 60
    #输出为字符串的另一种方式
    for i in dict:
    print(i,dict[i])

12. 字典的遍历