Ch 12 · Error Handling · Python

Topic 12 of 13 in Python — Complete Tutorial (Beginner) — 2 lessons.

try / except / finally

Programs face unpredictable situations: a user types text where a number was expected, a calculation divides by zero, a file is missing. These are runtime errors — they appear only while the program runs, because they depend on changing data. If unhandled, the program crashes with a confusing message. Good programs anticipate failure and handle it gracefully.

Raising Your Own Errors

You are not limited to catching errors Python throws — you can deliberately raise your own when your code detects an invalid situation, using the raise keyword followed by an error with a clear message. This is essential for validating input: when a function receives data that breaks its rules, raising an error immediately makes the problem visible, instead of letting bad data silently spread through your program.

All topics in Python Beginner

1. Introduction to Programming & Python
2. Your First Python Program
3. Variables — Your Data Containers
4. Data Types — Kinds of Values
5. Operators & Expressions
6. Conditional Statements
7. Loops & Iterations
8. Functions
9. Lists — Collections of Data
10. Dictionaries & Classes
11. Strings — Working with Text
12. Error Handling
13. Mini-Projects & Practice