Class 12 Python – Revision Notes (No Equations)

1. Basics of Python

• Python is a high-level, interpreted programming language.

• Case-sensitive: Variable and variable are different.

• Supports dynamic typing, meaning variables can store any data type.

• Indentation is important – it defines blocks of code.

2. Data Types

• Numeric types: int, float, complex

• Sequence types: list, tuple, string

• Set types: set, frozenset

• Mapping type: dictionary (key-value pairs)

• Boolean: True or False

• None: represents absence of value

3. Variables and Constants

• Variables store data values.

• Constants are fixed values that do not change.

• Python does not require explicit declaration; just assign a value.

4. Operators in Python

• Arithmetic operators: +, -, *, /, %, //, **

• Comparison operators: ==, !=, >, <, >=, <=

• Logical operators: and, or, not

• Assignment operators: =, +=, -=, *=, /=

• Membership operators: in, not in

• Identity operators: is, is not

5. Control Structures

• Conditional statements:

  • if, elif, else – used for decision making

• Loops:

  • for loop – iterate over sequences

  • while loop – execute until a condition is False

• Break and continue:

  • break – exits the loop immediately

  • continue – skips the current iteration

6. Functions

• Functions group reusable code for modular programming.

• Defining a function: Use def keyword.

• Calling a function: Use the function name followed by parentheses.

• Functions can return values or perform actions without returning.

• Arguments/Parameters: Inputs passed to functions.

7. Strings and String Operations

• Strings are sequences of characters enclosed in quotes.

• Can perform operations like:

  • Concatenation: joining strings

  • Repetition: repeating strings multiple times

  • Indexing: accessing individual characters

  • Slicing: extracting substrings

• Strings are immutable – cannot be changed once created.

8. Lists and Tuples

• List: Ordered, mutable collection of items

• Tuple: Ordered, immutable collection of items

• Operations include: adding, removing, updating elements (for lists), accessing elements using indexing and slicing

9. Dictionary and Sets

• Dictionary: Collection of key-value pairs; keys are unique

• Set: Unordered collection of unique elements

• Operations on sets: union, intersection, difference, membership check

10. File Handling

• Opening files: in read, write, append modes

• Reading files: read entire content or line by line

• Writing files: write or append data to a file

• Closing files: release the resource after use

11. Exception Handling

• Python uses try-except blocks to handle errors.

• Try block: contains code that may raise an exception

• Except block: handles the exception gracefully

• Prevents program crashes due to runtime errors

12. Object-Oriented Programming (OOP)

• Class: Blueprint for creating objects

• Object: Instance of a class

• Attributes: Properties of an object

• Methods: Functions defined inside a class

• Encapsulation: Keeping data safe inside objects

• Inheritance: A class can derive properties from another class

• Polymorphism: Same method can behave differently in different classes

13. Modules and Libraries

• Module: File containing Python code (functions, classes)

• Importing modules: Allows reuse of code

• Common libraries:

  • math – mathematical operations

  • random – generate random numbers

  • os – interact with the operating system

  • datetime – work with dates and times

14. Recap for Revision

• Python is high-level and dynamic

• Key concepts: variables, data types, control structures

• Important data structures: list, tuple, dictionary, set

• Modular programming: functions and modules

• File handling and exception handling

• Object-Oriented Programming: class, object, inheritance, polymorphism