List in Python Class 11 Notes | Python List Manipulation

  

What is List in Python?

• List is built in sequence data type in python.
• Stores multiple values
• List item can be of different data types
• All the items are comma separated and enclosed in square bracket.
• Individual item in a list can be accessed using index which begins from 0.

Examples

Accessing elements in a List

• Individual item in a list can be accessed using indexes.
• Indexes are unique numbers assigned to each item in a list to identify them
• Index always begins from 0 and written in square brackets “[]”.

Example:

List is Mutable

• Yes list is mutable.
• Content of the list can be changed after it has been created.

List operations

List supports following operations:

• Concatenation
• Repetition
• Membership
• Slicing

Concatenation

• Concatenation refers to joining two List.
• Plus (‘+’) is used as concatenation operator.
• Concatenating List with other data type produces TypeErrors.

Example:

Repetition

• Repetition as it name implies used to replicate a list at specified no of times.
• Asterisk (‘*’) is used as repetition operator.

Membership

• Membership operation refers to checking an item is exists in the list or not.
• Python uses ‘in’ and ‘not in’ as membership operator.
• ‘in’ returns true if the item specified present in the list.
• ‘not in’ returns true if the item specified present in the list.

Example:

Slicing

• Extracting a subset of items from given list is called slicing
• Subset occurred after slicing contains contiguous items.
• Slicing is done using index range like List[start_index : end_index : step_value]
• End index is always excluded in resultant subset of list.
• Negative index can also be used for slicing.

Examples:

Traversing a List

• Traversing a List refers to accessing each item a given list sequentially.
• for or while loop can be used for traversing a list.

Examples:

List methods | List Functions

Nested List

One list appears as an element inside another list.

Example: