1. Definition:

 A Python list is an ordered sequence of Heterogenous data type that are enclosed with Square Brackets and separated by commas.

Characteristics of a List

• Mutable: The elements within a list can be altered, added, or removed after the list is created.
• Ordered: The items have a defined sequence that does not change unless explicitly modified.
• Heterogeneous: A single list can contain elements of different data types, such as integers, floats, strings, tuples, or even other nested lists. It is highly useful for grouping mixed data.
• Zero-Indexed: List indices always start from 0 up to n-1 (where n is the number of elements).

Example

>>> list1 = [20, 5.5, 'hello']

>>> print(list1)

OUTPUT: [20, 5.5, 'hello']

2. List Indexing

Indexing allows you to access individual elements from the list.

• Positive Indexing: Starts from 0 for the very first element and goes up to n-1.
• Negative Indexing: Starts from -1 for the last element in the list and goes backwards down to -n.

Note: Attempting to access an index that does not exist will result in an Error.

Example :

>>> list1 = [20, 5.5, 'Hello']

>>> list1[0]      # OUTPUT: 20

>>> list1[2]      # OUTPUT: Hello

>>> list1[-1]     # OUTPUT: Hello  (last element)

>>> list1[-n]     # OUTPUT: 20     (first element)

>>> list1[5]      # OUTPUT: Error  (index out of range)

Operation	Syntax	Output
Concatenation	>>> [1,3,5,7,9] + [2,4,6,8,10]	[1,3,5,7,9,2,4,6,8,10]
Repetition	>>> ['Hello'] * 5	['Hello','Hello','Hello','Hello','Hello']
Membership (True)	>>> 'Amrit' in ['Varun','Ravindra','Amrit']	True
Membership (False)	>>> 'Nitin' in ['Varun','Ravindra','Amrit']	False