diff options
Diffstat (limited to 'Doc')
| -rw-r--r-- | Doc/library/contextlib.rst | 28 |
1 files changed, 17 insertions, 11 deletions
diff --git a/Doc/library/contextlib.rst b/Doc/library/contextlib.rst index 0b1f4f7..793bd63 100644 --- a/Doc/library/contextlib.rst +++ b/Doc/library/contextlib.rst @@ -47,22 +47,28 @@ Functions and classes provided: function for :keyword:`with` statement context managers, without needing to create a class or separate :meth:`__enter__` and :meth:`__exit__` methods. - A simple example (this is not recommended as a real way of generating HTML!):: + While many objects natively support use in with statements, sometimes a + resource needs to be managed that isn't a context manager in its own right, + and doesn't implement a ``close()`` method for use with ``contextlib.closing`` + + An abstract example would be the following to ensure correct resource + management:: from contextlib import contextmanager @contextmanager - def tag(name): - print("<%s>" % name) - yield - print("</%s>" % name) + def managed_resource(*args, **kwds): + # Code to acquire resource, e.g.: + resource = acquire_resource(*args, **kwds) + try: + yield resource + finally: + # Code to release resource, e.g.: + release_resource(resource) - >>> with tag("h1"): - ... print("foo") - ... - <h1> - foo - </h1> + >>> with managed_resource(timeout=3600) as resource: + ... # Resource is released at the end of this block, + ... # even if code in the block raises an exception The function being decorated must return a :term:`generator`-iterator when called. This iterator must yield exactly one value, which will be bound to |