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Python Programming Basics

Aug 27, 2025

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Overview

This lecture covers Python programming fundamentals, including setup, syntax, variables, strings, numbers, operators, loops, functions, and best practices. It introduces core concepts step by step for beginners aiming to use Python for a variety of applications.

Introduction to Python

  • Python is a popular, versatile programming language ideal for beginners and professionals.
  • Python is used in AI, machine learning, web development, data analysis, automation, and more.
  • Python code is concise and readable compared to other languages.
  • Major companies and diverse professions use Python.

Setting Up Python and Tools

  • Download Python from python.org and install the latest version.
  • Add Python to PATH during installation to avoid issues.
  • Use VS Code (or any preferred editor/IDE) for writing Python code.
  • Install the Python extension in VS Code for linting, debugging, and more.

Python Syntax and Basic Operations

  • Python code is interpreted by the Python interpreter (interactive shell/terminal).
  • Expressions are pieces of code that produce values (e.g., 2 + 2).
  • Syntax errors occur from incorrect grammar in code.

Writing and Running Python Code

  • Use the print() function to display output to the screen.
  • Python scripts have the .py extension and are run in terminal with python file.py.
  • Use VS Code integrated terminal or shortcuts to run files easily.

Code Quality Tools

  • Linting checks code for syntax/formatting errors before running.
  • Use the autopep8 formatter to enforce PEP 8 style guidelines.
  • Format code automatically on save for consistency and readability.

Python Implementations and Execution Model

  • CPython is the standard Python implementation; others include Jython and IronPython.
  • Python code is compiled to bytecode, then executed by the Python Virtual Machine.

Variables and Data Types

  • Variables store data in memory and act as labels for memory locations.
  • Python primitive types: integers (int), floating point numbers (float), booleans (bool), and strings (str).
  • Python is case-sensitive—True and False must be capitalized.

Naming Conventions and Best Practices

  • Use descriptive, lowercase variable names with underscores.
  • Separate multiple words with underscores; avoid abbreviations.
  • Space around assignment operators for clarity.

Working with Strings

  • Strings are surrounded by quotes (single, double, or triple).
  • Use len() to get string length; square brackets for indexing; slicing for substrings.
  • Escape sequences (e.g., \n for new line, " for double quote) control special characters inside strings.
  • Formatted strings (f-strings) allow embedding expressions.

String Methods

  • .upper(), .lower(), .title() change case; .strip() removes whitespace.
  • .find() locates substrings; .replace() substitutes text.
  • Use 'in' to check for substring existence.

Numbers and Arithmetic

  • Types: int, float, complex (a + bj).
  • Arithmetic operators: +, -, *, / (float div), // (integer div), % (modulus), ** (exponent).
  • Use round(), abs(), and the math module for numerical calculations.***

User Input and Type Conversion

  • Use input() to get user input (returns string).
  • Convert types using int(), float(), bool(), str().
  • In Python, some values are falsy (e.g., 0, empty string, None).

Comparison & Logical Operators

  • ==, !=, >, >=, <, <= compare values.
  • Logical operators: and, or, not combine conditions.
  • Short-circuit evaluation means the evaluation stops as soon as the result is determined.

Conditional Statements

  • Use if, elif, and else to control code flow based on conditions.
  • Indentation (4 spaces) is crucial for code blocks.
  • Ternary (conditional) expressions offer concise conditionals.

Loops

  • for loops iterate over ranges, strings, or lists.
  • range(start, stop, step) generates sequences of numbers.
  • Use break to exit loops early; else after a loop runs if the loop wasn't exited early.
  • Nested loops enable complex iterations.
  • while loops repeat as long as a condition is true; beware of infinite loops.

Functions

  • Define functions with def; parameters in parentheses.
  • Arguments are supplied when calling functions.
  • Functions either perform tasks (side effects) or return values.
  • Use return to send a value back from a function.
  • Default and keyword arguments make functions flexible.
  • Use args to accept a variable number of arguments (packed as a tuple).

Key Terms & Definitions

  • Interpreter — program that executes Python code.
  • Expression — code that produces a value.
  • Syntax Error — code with incorrect grammar.
  • Linter — tool to find code errors before execution.
  • PEP 8 — Python style guide for code formatting.
  • Variable — named reference to a value in memory.
  • String (str) — sequence of characters.
  • Boolean (bool) — value that is True or False.
  • Tuple — immutable ordered collection, defined with parentheses.
  • Iterable — object that can be looped over.
  • Function — reusable block of code with optional parameters and a return value.
  • Parameter — variable in function definition.
  • Argument — actual value supplied to function parameter.
  • Keyword Argument — argument passed by name.
  • Default Parameter — function parameter with a default value.

Action Items / Next Steps

  • Download and install Python and VS Code.
  • Install the Python extension and autopep8 formatter in VS Code.
  • Practice writing basic programs using variables, strings, numbers, and input/output.
  • Complete exercises on conditional statements, loops, and functions as shown in the lecture.
  • Review PEP 8 for additional style guidelines.
  • Next: Learn about data structures and advanced programming concepts.

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