Python for Data Analytics • Lesson 18

Errors, Debugging & Exceptions

Learn how to understand Python errors, find bugs, debug your programs, and handle common runtime problems using try and except.

Your progress0%

0 of 8 concepts completed

Complete the activity and related MCQ to unlock the next concept.

Concept 1ERRORS

What Is an Error?

An error occurs when Python cannot execute your code as written. Errors are normal — the skill is reading the message, finding the line, and fixing the cause.

Learn by Seeing

Read the message first

print("Hello"
# SyntaxError: '(' was never closed

The closing parenthesis is missing, so Python cannot parse the line.

Syntax

code won't parse

Runtime

fails while running

Logical

runs, wrong result

Interactive Activity

What is the fastest first step when Python shows an error?

Hint: The message tells you what went wrong and where.

Python Analyst Mindset

Debugging is a daily skill, not a special event

Every analyst reads error messages every day. The faster you can classify the failure — syntax, runtime or logical — and reach for the right fix, the faster you can move from raw data to a trustworthy result.

Read

The message names the problem.

Locate

The line number points at the area.

Classify

Syntax, runtime or logical?

Fix

Apply the smallest correct change.

Mini-Project

Safe CSV Row Parser

You receive sales rows as strings — some are clean numbers, some are malformed. Wrap the conversion in try/except so a bad row is skipped without crashing the whole report.

rows = ["1200", "980", "abc", "1500", "", "2100"]
total = 0

for row in rows:
    try:
        total += int(row)
    except ValueError:
        print(f"Skipping bad row: {row!r}")

print("Total sales:", total)
# Skipping bad row: 'abc'
# Skipping bad row: ''
# Total sales: 5780

This is the exact pattern used in real data pipelines — one bad value must never sink an entire batch. try/except + ValueError is the smallest tool that does the job.

Lesson Summary

What you learned

Syntax error

Code breaks Python's grammar.

Runtime error

Fails while the program runs.

Logical error

Runs, but produces the wrong result.

NameError / TypeError / IndexError

Common built-in runtime errors.

try / except

Catch an expected exception without crashing.

Debugging process

Read → locate → classify → fix → re-run.

Frequently Asked Questions