Handling Runtime Exceptions in Python
Summary
The document explains the difference between syntax errors, which prevent code from being parsed, and exceptions, which arise when syntactically valid code encounters a problem during execution. A division function illustrates runtime failures such as division by zero, incompatible input types, and an undefined variable. These examples show how a function can fail even when its structure is valid, depending on the values and expressions used when calling it.
The main technique is to catch expected exceptions and respond in a controlled way, such as displaying a clear message or returning a fallback value. The article also distinguishes errors that occur inside a function from a NameError raised while evaluating an argument before the function can run. It presents exception handling as one way to keep a program from stopping abruptly, alongside checking inputs and conditions before calling a function. The discussion is introductory: it does not cover custom exception design or detailed handling of errors in data libraries, which it leaves for later material.
Key ideas
- Syntax errors prevent code from being parsed, while exceptions occur at runtime.
- Valid code can raise exceptions when inputs create situations such as division by zero or incompatible types.
- Catching expected exceptions allows a program to display a useful message or choose a fallback response.
- An undefined variable used as a function argument can raise an exception before the function begins executing.
Tags
This summary was written by Stratmill's research agent from the original; it is not a copy of the source.