Python List

List

Lists are used to store multiple items in a single variable.

Lists are one of 4 built-in data types in Python used to store collections of data, the other 3 are Tuple, Set, and Dictionary, all with different qualities and usage.

Lists are created using square brackets:

Example

Create a List:

 
thislist = ["apple", "banana", "cherry"]

print(thislist)

List Items

List items are ordered, changeable, and allow duplicate values.

List items are indexed, the first item has index [0], the second item has index [1] etc.

Ordered

When we say that lists are ordered, it means that the items have a defined order, and that order will not change.

If you add new items to a list, the new items will be placed at the end of the list.

Note: There are some list methods that will change the order, but in general: the order of the items will not change.

Changeable

The list is changeable, meaning that we can change, add, and remove items in a list after it has been created.

Allow Duplicates

Since lists are indexed, lists can have items with the same value:

Example

Lists allow duplicate values:

 
thislist = ["apple", "banana", "cherry", "apple", "cherry"]

print(thislist)

List Length

To determine how many items a list has, use the len() function:

Python Lists

Lists are just like dynamic sized arrays, declared in other languages (vector in C++ and ArrayList in Java). Lists need not be homogeneous always which makes it a most powerful tool in Python. A single list may contain DataTypes like Integers, Strings, as well as Objects. Lists are mutable, and hence, they can be altered even after their creation.

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. Each element in the list has its definite place in the list, which allows duplicating of elements in the list, with each element having its own distinct place and credibility.

Note- Lists are a useful tool for preserving a sequence of data and further iterating over it.

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Creating a List

Lists in Python can be created by just placing the sequence inside the square brackets[]. Unlike Sets, list doesn’t need a built-in function for creation of list.

Note – Unlike Sets, list may contain mutable elements.

 # Python program to demonstrate 
# Creation of List 
  
# Creating a List
List=[]
print("Blank List: ")
print(List)
  
# Creating a List of numbers
List=[10, 20, 14]
print("\nList of numbers: ")
print(List)
  
# Creating a List of strings and accessing
# using index
List=["Geeks", "For", "Geeks"]
print("\nList Items: ")
print(List[0]) 
print(List[2])
  
# Creating a Multi-Dimensional List
# (By Nesting a list inside a List)
List=[['Geeks', 'For'] , ['Geeks']]
print("\nMulti-Dimensional List: ")
print(List)

For more, checkout W3Schools and Geeks For Geeks.