Python Class Notes

1. Features of Python

• Simple & Easy to Learn: Python has a clean and readable syntax.
• Freeware & Open Source: It is freely available and open-source.
• Dynamically Typed: No need to declare variable types explicitly.
• Interpreted: Python executes code line-by-line.
• High-Level & Robust: Python provides memory management and strong error handling.

2. Comments in Python

• Single-line Comment: Uses # (e.g., # This is a comment).
• Multi-line Comment: Uses triple quotes """ ... """ or ''' ... '''.
• Comments help in documentation and code readability.

3. Python Keywords

• Control Flow: if, else, elif, for, while, break, continue, pass.
• Exception Handling: try, except, finally, raise.
• Functions & Modules: def, return, import, from, lambda.
• Other Keywords: True, False, None, global, nonlocal, yield.

4. Identifiers & Case Styles

• Identifiers: Variable names must start with a letter (A-Z or a-z) or _ and cannot be a keyword.
• Case Sensitivity: Python is case-sensitive (abc and ABC are different).
• Valid Identifiers: myVar, _my_var, abc123.
• Invalid Identifiers: 123abc, for (reserved keyword).
• Naming Conventions:
  • camelCase: myVariableName
  • PascalCase: MyClassName
  • snake_case: my_variable_name
  • kebab-case: Not used in Python (my-variable-name is invalid).

5. Arithmetic & Assignment Operators

• Arithmetic Operators: +, -, *, /, // (floor division), % (modulus), ** (exponent).

• Assignment Operators: =, +=, -=, *=, /=, %=, **=.

• Example:

  x = 5  
  y = 2  
  print(x + y)  # Output: 7  
  x *= y  # Equivalent to x = x * y  
  print(x)  # Output: 10