Test your knowledge: contextlib.ExitStack

Review

1. Which ExitStack method enters a context manager and registers its exit operation?

   Use enter_context() when the stack should enter the manager now and later exit it.
2. In what order does ExitStack run registered cleanup operations?

   Cleanup unwinds in reverse registration order, matching nested context managers.
3. A second file open raises FileNotFoundError after the first file was entered through the stack. What happens to the first file?

   The stack has already registered the first file’s exit operation, so it runs when the block unwinds.
4. Can a function registered with stack.callback() suppress the active exception?

   callback() calls a normal function with the arguments you supplied, not the exception triple. Use an appropriate context manager if suppression is truly intended.
5. What does pop_all() do?

   The returned stack becomes the owner; it must later be closed or used in a with statement.
6. When is ExitStack usually most helpful?

   A regular with statement is simpler for fixed resources; ExitStack is useful for dynamic or staged acquisition.
7. Which method should you await to enter an asynchronous context manager through AsyncExitStack and register its exit operation?

   Use await stack.enter_async_context(manager). AsyncExitStack also supports synchronous managers through enter_context(), but those use their ordinary synchronous entry and exit methods.