Python如何使用Collections.UserDict？代码示例

用于存储数据值(如Map)的无序数据值集合称为Python字典。与仅包含单个值作为元素的其他数据类型不同, 字典具有核心价值对。字典中提供了键值以使其更优化。

注意：有关更多信息, 请参阅Python字典

Collections.UserDict

Python支持字典就像一个叫做UserDict存在于collections模块。此类充当字典对象周围的包装器类。当一个人想要创建自己的具有某些修改功能或某些新功能的字典时, 此类非常有用。它可以被视为为字典添加新行为的一种方式。此类将字典实例作为参数, 并模拟保存在常规字典中的字典。该类的data属性可访问该词典。

语法如下：

collections.UserDict([initialdata])

范例1：

# Python program to demonstrate
# userdict
  
  
from collections import UserDict
  
  
d = { 'a' : 1 , 'b' : 2 , 'c' : 3 }
  
# Creating an UserDict
userD = UserDict(d)
print (userD.data)
  
  
# Creating an empty UserDict
userD = UserDict()
print (userD.data)

输出如下：

{'a': 1, 'b': 2, 'c': 3}
{}

范例2：让我们创建一个从UserDict继承的类, 以实现自定义词典。

# Python program to demonstrate
# userdict
   
  
from collections import UserDict
   
  
# Creating a Dictionary where
# deletion is not allowed
class MyDict(UserDict):
      
     # Function to stop deleltion
     # from dictionary
     def __del__( self ):
         raise RuntimeError( "Deletion not allowed" )
          
     # Function to stop pop from 
     # dictionary
     def pop( self , s = None ):
         raise RuntimeError( "Deletion not allowed" )
          
     # Function to stop popitem 
     # from Dictionary
     def popitem( self , s = None ):
         raise RuntimeError( "Deletion not allowed" )
      
# Driver's code
d = MyDict({ 'a' : 1 , 'b' : 2 , 'c' : 3 })
  
print ( "Original Dictionary" )
print (d)
  
d.pop( 1 )

输出如下：

Original Dictionary
{'a': 1, 'c': 3, 'b': 2}

Traceback (most recent call last):
  File "/home/3ce2f334f5d25a3e24d10d567c705ce6.py", line 35, in 
  
   
    d.pop(1)
  File "/home/3ce2f334f5d25a3e24d10d567c705ce6.py", line 20, in pop
    raise RuntimeError("Deletion not allowed")
RuntimeError: Deletion not allowed
Exception ignored in: 
   
    
Traceback (most recent call last):
  File "/home/3ce2f334f5d25a3e24d10d567c705ce6.py", line 15, in __del__
RuntimeError: Deletion not allowed

首先, 你的面试准备可通过以下方式增强你的数据结构概念：Python DS课程。

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