Introduction to Python and Basic Concepts

Overview

This lecture covers the basic introduction to the Python language, syntax, variables, data types, operators, input-output, type conversion, and some basic practice questions.

Introduction to Python

• Python is a simple, open-source, high-level, and versatile programming language.
• Coders use Python in web development, machine learning, data science, etc.
• Python is easy to learn and looks like English.
• An interpreter is used to translate Python into machine-level language.

Python Installation and Setup

• Python can be downloaded from python.org; check the necessary boxes during installation.
• Check the version on both Windows/Mac using the command python --version.
• Use Visual Studio Code (VS Code) editor for writing code.

Basic Concepts

• Meaning of programming: giving instructions to the machine, called code.
• Process: Code (high-level language) → Translator → Machine language (0,1)
• Character set: English letters, digits (0-9), special symbols, whitespace are valid.

Variables and Data Types

• Variables: the name of a memory location where data is stored.
• Assignment: variable = value like age = 23
• Data types:
  • int (integer): whole numbers (like 5, -5, 0)
  • float: decimal numbers (like 4.5)
  • str (string): words or sentences (like "Python")
  • bool (boolean): True/False
  • None: no value

Variable Naming Rules

• Names can include letters, digits, underscore (_); digits cannot start the name.
• Special symbols and keywords (like True, None, False) cannot be used in variable names.
• Keep variable names simple, short, and meaningful._

Keywords and Case Sensitivity

• Python has fixed keywords with fixed meanings.
• Python is case sensitive; name and Name are considered different.

Output (print) and Input (input)

• print() is used to display output on the screen.
• input() takes data from the user; input always takes a string, so type casting is necessary.
• Type casting: int(input()), float(input()), str(val), etc.

Operators

• Arithmetic operators: +, -, *, /, %, **
• Comparison operators: ==, !=, >, <, >=, <=
• Assignment operators: =, +=, -=, *=, /=, %=, **=
• Logical operators: not, and, or

Comments

• Use # for single-line comments, ''' or """ for multi-line comments.
• Comments explain the code and do not run.

Type Conversion and Casting

• Python automatically converts int to float (implicit conversion).
• Manual type casting is done using int(), float(), str().

Practice Questions

• Take two numbers as input and print their sum.
• Take the side of a square as input and print its area.
• Take two floating-point numbers as input and print their average.
• Take two integers as input and print True if the first is greater than or equal to the second, otherwise False.

Key Terms & Definitions

• Variable — the name of memory where the value is stored.
• Data Type — the type of data stored in a variable; int, float, str, bool, None.
• Keyword — reserved words that cannot be used as variable names.
• Type Casting — converting one type to another.
• Operator — a symbol that performs operations on values (like +, -).
• Comment — used to explain code, does not run.

Action Items / Next Steps

• Install VS Code and Python.
• Write and run basic programs (sum, area, average) yourself.
• Download lecture notes/slides from the description.
• Explore for the next lecture: Conditional Statements (if-else).