All 15 Exception Handling questions
More in Exception Handling
What does the 'finally' block guarantee, and when is it typically used? How do you catch multiple exception types with a single except clause? Why is a bare 'except:' clause (catching everything with no type specified) generally discouraged? How do you create a custom exception class, and what's the minimal amount of code needed? What is the difference between 'raise' and 'raise ... from ...' for exception chaining? How do you access details about the exception currently being handled, like its type, value, and traceback, using sys.exc_info()? How does the 'else' clause on a try statement work, and what's its purpose compared to just putting that code at the end of 'try'? How does Python 3.11's exception groups (ExceptionGroup) and the 'except*' syntax let you handle MULTIPLE unrelated exceptions raised together? How would you design a custom exception HIERARCHY for an application, and why does this matter for how callers can catch errors at different granularities? How does context manager __exit__ interact with exception handling, and how can it SUPPRESS an exception by returning True?
Advertisement
Python › Exception Handling

How does a try/except block work, and what happens if no matching except clause exists?

Beginner

Answer

Code in 'try' runs normally; if it raises an exception, Python looks for the FIRST 'except' clause matching that exception's type (checked top to bottom) and runs it — if none match, the exception propagates up the call stack, potentially crashing the program if never caught anywhere.
try:
    result = 10 / 0
except ZeroDivisionError:
    print("Cannot divide by zero")
except ValueError:
    print("Invalid value")
Real-world example Gracefully handling a division-by-zero or invalid-input error instead of letting the program crash with an unhandled traceback.

Common follow-ups: What happens if you put a more GENERAL exception type's except clause BEFORE a more SPECIFIC one?

Data Types & Structures
All 15 Exception Handling questions