'with' statement for StringIO (Python)

2009-02-24T00:01:16-08:00

Python recipe 576650 by srid (stringio, with_statement). Revision 3.

NOTE: Consider this recipe obsolete. Instead use contextlib.closing (see comment below).

This contextmanager adds 'with' statement support for StringIO. Peruse the following simple example:

with StringIO() as sio:
    function_accepting_file_handle(sio)
    print sio.getvalue()

Use PDFWriter with context manager support (Python)

2013-12-16T21:43:27-08:00

Python recipe 578790 by Vasudev Ram (contextmanager, context_manager, pdf, python, reportlab, with_statement, xtopdf).

PDFWriter - a core class of the xtopdf toolkit - can now be used with a Python context manager, a.k.a. the Python with statement.

Code example below. More details here:

http://jugad2.blogspot.in/2013/12/xtopdf-pdfwriter-now-has-context.html

Wrap any iterable context manager so it closes when consumed (Python)

2012-11-19T20:10:35-08:00

Python recipe 578342 by Andrew Barnert (contextmanager, context_manager, generator, iterable, iterator, with_statement).

There are a few types in Python—most notably, files—that are both iterators and context managers. For trivial cases, these features are easy to use together, but as soon as you need to use the iterator lazily or asynchronously, a with statement won't help. That's where this recipe comes in handy:

send_async(with_iter(open(path, 'r')))

This also allows you to "forward" closing for a wrapped iterator, so closing the outer iterator also closes the inner one:

sync_async(line.upper() for line in with_iter(open(path, 'r')))

Decorator and context manager from a single API (Python)

2010-06-27T15:15:01-07:00

Python recipe 577273 by Michael Foord (contextmanager, context_manager, decorator, decorators, with, with_statement). Revision 12.

Create objects that act as both context managers and as decorators, and behave the same in both cases.

Works with Python 2.4 - 2.7 and Python 3. The tests require unittest2 or Python 3.2 to run. (And because the tests use the with statement they won't work with Python 2.4.)

Example:

from contextdecorator import ContextDecorator

class mycontext(ContextDecorator):

    def __init__(self, *args):
        """Normal initialiser"""

    def before(self):
        """
        Called on entering the with block or starting the decorated function.

        If used in a with statement whatever this method returns will be the
        context manager.
        """

    def after(self, *exc):
        """
        Called on exit. Arguments and return value of this method have
        the same meaning as the __exit__ method of a normal context
        manager.
        """

Both before and after methods are optional (but providing neither is somewhat pointless). See the tests for more usage examples.

Temporary substitution of object in modules via with statement (Python)

2010-01-24T04:19:12-08:00

Python recipe 577020 by Jacob Oscarson (modules, testing, with_statement).

See docstring in the code

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