Collections.UserList in Python

Python Lists are array-like data structure but unlike it can be homogeneous. A single list may contain DataTypes like Integers, Strings, as well as Objects. List in Python are ordered and have a definite count. The elements in a list are indexed according to a definite sequence and the indexing of a list is done with 0 being the first index. 
Note: For more information, refer to Python List
 

Collections.UserList

Python supports a List like a container called UserList present in the collections module. This class acts as a wrapper class around the List objects. This class is useful when one wants to create a list 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 list. This class takes a list instance as an argument and simulates a list that is kept in a regular list. The list is accessible by the data attribute of the this class.
Syntax:
 

collections.UserList([list])

Example 1:
 

# Python program to demonstrate # userlist from collections import UserList L = [1, 2, 3, 4] # Creating a userlist userL = UserList(L) print(userL.data) # Creating empty userlist userL = UserList() print(userL.data) 

Output:
 

[1, 2, 3, 4] []

The time complexity of this Python program is O(n), where n is the length of the input list L.

 The auxiliary space used by this program is O(n), where n is the length of the input list L.
 

# Python program to demonstrate # userlist from collections import UserList # Creating a List where # deletion is not allowed class MyList(UserList): # Function to stop deletion # from List def remove(self, s = None): raise RuntimeError("Deletion not allowed") # Function to stop pop from  # List def pop(self, s = None): raise RuntimeError("Deletion not allowed") # Driver's code L = MyList([1, 2, 3, 4]) print("Original List") # Inserting to List" L.append(5) print("After Insertion") print(L) # Deleting From List L.remove() 

Output:
 

Original List After Insertion [1, 2, 3, 4, 5]

Traceback (most recent call last): File "/home/9399c9e865a7493dce58e88571472d23.py", line 33, in L.remove() File "/home/9399c9e865a7493dce58e88571472d23.py", line 15, in remove raise RuntimeError("Deletion not allowed") RuntimeError: Deletion not allowed