Errors and exceptions

Why it matters

Code that talks to the outside world fails in ordinary ways all the time: a file is missing, an API times out, a model returns text that isn't valid JSON. What separates a fragile script from a reliable tool is how it handles those failures. Reading a traceback quickly is also the fastest debugging skill there is, whether you wrote the code or an AI assistant did.

What you'll be able to do

• Read a traceback from the bottom up and find the line that failed
• Recognize the common exception types and what usually causes each
• Handle an expected failure with try and except, plus else and finally
• Raise your own exception when a function gets input it can't use

Before this lesson

• Functions

Next in this phase: Modules and imports