Collections.UserDict in Python

An unordered collection of data values that are used to store data values like a map is known as Dictionary in Python. Unlike other Data Types that hold only a single value as an element, Dictionary holds key:value pair. Key-value is provided in the dictionary to make it more optimized.

Note: For more information, refer to Python Dictionary

Collections.UserDict

Python supports a dictionary like a container called UserDict present in the collections module. This class acts as a wrapper class around the dictionary objects. This class is useful when one wants to create a dictionary of their own with some modified functionality or with some new functionality. It can be considered as a way of adding new behaviors to the dictionary. This class takes a dictionary instance as an argument and simulates a dictionary that is kept in a regular dictionary. The dictionary is accessible by the data attribute of this class.

Syntax: 

collections.UserDict([initialdata])

Example 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) 

Output:

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

Example 2: Let's create a class inheriting from UserDict to implement a customized dictionary.

# Python program to demonstrate # userdict from collections import UserDict # Creating a Dictionary where # deletion is not allowed class MyDict(UserDict): # Function to stop deletion # 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) 

Output:

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