Resource management

Ensures safe handling of multiple context managers with variable or conditional entry, guaranteeing cleanup.

Opening a variable number of files based on user input; managing plugin lifecycles where each plugin provides a context manager; cleaning up resources in test fixtures with conditional setups.

Python standard library code, testing frameworks, plugin systems, any scenario requiring dynamic resource management.

with contextlib.ExitStack() as stack:

with contextlib.ExitStack() as ...:

stack: variable name for the ExitStack instance

• stack.enter_context(cm)
• stack.callback(func)
• stack.pop_all()

• Nested with statements
• try/finally blocks
• contextlib.nested (deprecated)

Assuming ExitStack automatically cleans up resources without using it as a context manager; forgetting to call stack.close() when not used with 'with'.

Multiple nested with statements (static); contextlib.nested (deprecated, limited to two).

Coming from C#: using statement; Java: try-with-resources – those handle fixed resources, not dynamic stacks.

• contextlib.contextmanager
• contextlib.suppress
• try/finally
• AsyncExitStack

ExitStack does not suppress exceptions; if an entered context manager raises, __exit__ of all previously entered managers is still called. It also supports async via AsyncExitStack.

Guarantees cleanup of a dynamic set of resources, reducing nesting and improving readability.

Think of a stack of plates you can push and pop as needed.

ExitStack does not suppress exceptions; it guarantees cleanup of all entered context managers even if some raise exceptions.

AsyncExitStack for asynchronous context managers.