How to effectively manage resource cleanup when using Python's context managers with custom classes?
I've spent hours debugging this and I'm wondering if anyone has experience with I'm getting frustrated with I'm sure I'm missing something obvious here, but I'm working on a Python application where I'm using custom context managers to handle file operations... I'm working with issues with resource cleanup, especially when exceptions occur. Here's a simplified version of my context manager: ```python class FileHandler: def __init__(self, filename): self.filename = filename self.file = None def __enter__(self): self.file = open(self.filename, 'r') return self.file def __exit__(self, exc_type, exc_value, traceback): if self.file: self.file.close() ``` I use it like this: ```python with FileHandler('test.txt') as f: data = f.read() ``` The question arises when I have a logic behavior in my reading code, such as trying to read past the end of the file, which raises an exception. In this case, I notice that the file does not close properly. I also tried adding explicit cleanup in the `__exit__` method, but that didn't seem to help. The behavior I get is: `ValueError: I/O operation on closed file`. I want to ensure that the file is always closed, regardless of whether an exception occurs. What can I do to fix this? Any additional best practices for resource management in Python would be appreciated. Am I missing something obvious? Thanks for taking the time to read this! This is part of a larger application I'm building. Thanks for any help you can provide! I'm developing on CentOS with Python.