5.4 Error Handling and Automation | Code Scholars Tutoring

How it works

Exception handling separates the expected path from the recovery path. Catching everything hides the bugs you needed to see.

Catch the specific exception you can actually recover from, and let the rest surface.

Common error

A bare catch-all that swallows genuine errors and turns a crash into wrong output.

Worked example

Python

values = ["3", "bad", "5"]
total = 0
for value in values:
    try:
        total += int(value)
    except ValueError:
        print("skipped", value)
print(total)

Output

skipped bad
8

Catch the specific failure expected at the conversion boundary. The program should expose skipped work or another defined outcome rather than silently hiding every possible error.

Exercises

5.4.1 · Explain

Why is an unrestricted except block risky in an automation script?

Show solution

It can hide unrelated programming mistakes and make failed work look successful. Catch expected exceptions and report or propagate other failures.

5.4.2 · Write code

Convert ["2", "x", "4"] into integers, skipping invalid entries, and print the result.

Show solution

Handle ValueError at the individual conversion.

One valid solution

result = []
for value in ["2", "x", "4"]:
    try:
        result.append(int(value))
    except ValueError:
        continue
print(result)

Expected output

[2, 4]

Open Python compiler