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:
Python3
from collections import UserList
L = [ 1 , 2 , 3 , 4 ]
userL = UserList(L)
print (userL.data)
userL = UserList()
print (userL.data)
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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.
Python3
from collections import UserList
class MyList(UserList):
def remove( self , s = None ):
raise RuntimeError( "Deletion not allowed" )
def pop( self , s = None ):
raise RuntimeError( "Deletion not allowed" )
L = MyList([ 1 , 2 , 3 , 4 ])
print ( "Original List" )
L.append( 5 )
print ( "After Insertion" )
print (L)
L.remove()
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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