How to Handle AssertionError in Python: Displaying a Custom Error Message

Learn how to gracefully handle `AssertionError` exceptions in Python when dealing with financial data, and improve your code by displaying a concise error message.
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Handling AssertionError in Python: Displaying a Custom Error Message

When working with APIs, especially in finance, it's common to encounter issues such as missing or invalid data. In this post, we'll address a specific problem encountered in Python code while attempting to retrieve stock data using the yahoo_fin library. The goal is to understand how to effectively manage AssertionError exceptions and cleanse our output to show only the relevant error messages.

The Problem: Lack of Clarity in Error Messaging

In the provided code snippet, if an AssertionError occurs—specifically when the ticker symbol is not found—we want to present a more user-friendly error message. The code currently prints a verbose error message, which might not be helpful for users unfamiliar with the technicalities of API responses.

Here's the original code:

[[See Video to Reveal this Text or Code Snippet]]

The exception we'll focus on is structured in a way that includes a lot of additional information that we may not need.

The Solution: Refined Code Implementation

Key Improvements

String Checking: Instead of checking for just a part of the error message, we should check for the entire relevant string: "No data found, symbol may be delisted".

Redundant Code Removal: The brackets used in the if statement are unnecessary and can be removed for cleaner code.

Unused Imports: If any modules are not utilized in the code, they should be removed to enhance performance and readability.

Formatting Improvements: Enhancing code readability improves maintainability and collaboration.

Improved Code Example

Here’s an optimized version of the original code:

[[See Video to Reveal this Text or Code Snippet]]

Breakdown of Changes

Full Error String Check: The condition now checks for the complete error message, ensuring accuracy in determining the error type.

Simplified Condition: The removal of unnecessary parentheses around the if condition leads to cleaner and more efficient code.

Elimination of Unused Imports: This helps streamline your code, allowing Python to focus resources only on what's necessary.

Conclusion

Handling exceptions gracefully in your Python code not only improves user experience but also helps maintain clean and efficient code structure. By following the enhancements discussed, you can ensure that any user-facing error messages are clear and concise, ultimately leading to a more robust application.

Next time you encounter an AssertionError, refer back to these tips to simplify your error handling and make your code cleaner and more user-friendly. Happy coding!