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