Python Lists are array-like data structure but unlike it can be homogenous. 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] []
Example 2:
# Python program to demonstrate # userlist from collections import UserList # Creating a List where # deletion is not allowed class MyList(UserList): # Function to stop deleltion # 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) # Deliting 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, inL.remove() File "/home/9399c9e865a7493dce58e88571472d23.py", line 15, in remove raise RuntimeError("Deletion not allowed") RuntimeError: Deletion not allowed
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