An unordered collection of data value that is used to store data values like a map is known as Dictionary in Python. Unlike other Data Types that hold only 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 for 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 inherting from UserDict to implement a customised dictionary.
# 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) |
Output:
Original Dictionary
{'a': 1, 'c': 3, 'b': 2}
Traceback (most recent call last): File "/home/3ce2f334f5d25a3e24d10d567c705ce6.py", line 35, ind.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
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