Working with Modules and Handling Exceptions

Estimated study time: 11 minutes.

Two skills separate beginner code from production-ready code: organizing logic into modules, and anticipating failure with proper exception handling.

Working with Modules

A module is simply a single file containing related code — functions, classes, or variables — that can be imported elsewhere. Splitting a project into modules makes it easier to test, debug, and reuse individual pieces.

# file: calculator.py
def add(a, b):
    return a + b

# file: main.py
from calculator import add
print(add(4, 5))

Handling Exceptions

Not every operation succeeds — a file might not exist, a network call might time out, or user input might be invalid. Exception handling lets your program respond gracefully instead of crashing.

try:
    result = 10 / 0
except ZeroDivisionError as e:
    print("Cannot divide by zero:", e)
finally:
    print("Cleanup runs regardless of the outcome.")

Best Practices

• Catch specific exception types rather than a bare except.
• Use finally for cleanup code that must always run.
• Don't use exceptions for routine control flow — reserve them for genuinely exceptional cases.