How to properly close resources in case of errors?

Properly closing system resources when errors occur is a fundamental requirement to ensure stability, security, and the absence of memory leaks or file descriptors in Python applications. The most reliable and recommended way to manage resources in the language is to use context managers with the with keyword, which guarantees resource release regardless of whether the code block completed successfully or raised an exception.

If your code needs to work with multiple independent resources simultaneously, modern syntax allows combining them in a single with statement separated by commas, or using the convenient contextlib module for more complex scenarios. This spares the developer from having to manually write cumbersome and error-prone try-finally constructs for every opened file or network connection.

However, in situations where you are working with third-party libraries or legacy code that do not support the context manager protocol, the classic try-finally construct remains indispensable for reliably closing connections. Potentially dangerous operations are performed in the try block, errors are caught and logged with full exception context preservation in the except block, and resource closing methods are guaranteed to be called in the finally block.

Following these simple rules prevents accidental exhaustion of the operating system's open descriptor limit, database freezes due to unclosed cursors, and data corruption in files. Professional code is always designed with the expectation that any I/O operation can fail, and resources must be returned to the system in any situation.