Python basic

 

Python Basics Summary

1. Hello World Program

   • Use print("Hello, World!") to display text.

2. Syntax Errors

   • Occur when Python can't understand your code due to incorrect structure.
   • Example: missing brackets, colons, or using wrong keywords.
   • print("Hello"  # ❌ SyntaxError: missing closing parenthesis
   
   
3. Variable Naming Rules
1. Must start with a letter or underscore (_)
2. Can include letters, numbers, and underscores
3. Cannot use Python keywords (like class, if, def)
4. Case-sensitive (Name ≠ name)

5. student_name = "Aisha"  # ✅ Valid
   1name = "Ben"           # ❌ Invalid

4. Using Variables

   • Variables store data like text, numbers, or results of calculations.

   • name = "Aisha"
     score = 85
     total = score + 10

5. Input from Command Prompt
1. Use input() to get user input.
2. Always returns a string, so convert to int or float if needed.

3. name = input("Enter your name: ")
   age = int(input("Enter your age: "))

6. Comments in Python

• Used to explain code or leave notes.
• Single-line: # This is a comment
• Multi-line: ''' This is a multi-line comment '''
• 

7. Data Types
1. str: text (e.g., "Hello")
2. int: whole numbers (e.g., 10)
3. float: decimal numbers (e.g., 3.14)

8. Assignment Statements

   • Use = to assign values to variables.

9. If-Else Statements

   • Make decisions using if, elif, and else.

   • score = 75
     if score >= 50:
         print("Pass")
     else:
         print("Fail")

10. BIDMAS Rule in Arithmetic

    • Python follows Brackets, Indices, Division, Multiplication, Addition, Subtraction.

    • result = (3 + 2) * 4 ** 2 / 2 - 5

11. Comparison Operators

    • ==, !=, >, <, >=, <= for comparing values.

12. Indentation

    • Python uses indentation to define blocks of code (e.g., inside if, for, def).

13. Types of Errors

    • Syntax Error: Code structure mistake
    • Runtime Error: Error during execution (e.g., divide by zero)
    • Logic Error: Code runs but gives wrong result

14. Loops

    • for loop: repeat a known number of times

    • for i in range(5):
          print(i)

    • while loop: repeat while a condition is true

    • count = 1
      while count <= 5:
          print(count)
          count += 1