Python Basics Overview

Overview

This lecture is a quick-start guide to Python basics, focusing on variables, data types, printing, logic, loops, functions, and error handling.

Setting Up Python and Tools

• Use Python 3.8 and PyCharm editor to write and run Python code.
• Both Python and PyCharm are free and open-source.

Variables & Naming

• Assign a value to a variable using the equals sign (e.g., item = "banana").
• Python is case sensitive: item and Item are different variables.
• Use underscores for multi-word variable names (e.g., item_name = "orange").

Data Types and Printing

• Data types: integer (e.g., 10), string (e.g., "apple"), boolean (True/False), list (e.g., ["a", "b"]).
• Print values using the print() function.
• Combine strings and variables using +, but convert data types as needed (str(), int()).

Type Conversion and Exceptions

• Convert integers to strings with str() for combining with text.
• Convert string numbers to integers with int() before doing math.
• Type mismatches cause exceptions.

Basic Math Operations

• Addition: +
• Subtraction: -
• Multiplication: *
• Division: /
• Exponentiation: ***

Logic Statements (If/Else)

• Use if, elif, else to write conditional logic based on variable values.
• Example: if age > 21: print("You are old")

Loops

• For loop: for i in range(3): repeats three times (indexes start at 0).
• For loops can also iterate over lists.
• While loop: continues as long as a condition is true (e.g., while i < 5).
• Use break to exit a loop early.

User Input

• Get user input with input(), which returns a string.
• Use while True for infinite loops; break on a specific input to stop.

Functions

• Define a function with def (e.g., def say_hello(name):).
• Functions help you reuse code by running the same logic with different inputs.
• Use pass as a placeholder for function bodies not yet implemented.

Error Handling (Try/Except)

• Use try and except blocks to catch and handle errors (exceptions) in your code.
• Example: Handle invalid user input and print an error message instead of stopping the program.

Key Terms & Definitions

• Variable — a named storage for a value.
• String — text enclosed in quotes.
• Integer — whole number data type.
• Boolean — True or False value.
• List — ordered collection of items.
• Function — reusable block of code defined with def.
• Exception — an error detected during code execution.

Action Items / Next Steps

• Install Python 3.8 and PyCharm.
• Practice writing and running basic Python scripts covering the topics above.