Context manager for restoring a value (Python)

2010-01-09T07:14:06-08:00

Python recipe 576977 by George Sakkis (contextlib, context_manager). Revision 8.

Often one wants to rebind a name or modify a mutable object, perform a bunch of actions and finally restore the name/object to its original state. An example is redirecting stdout/stderr temporarily (http://www.diveintopython.org/scripts_and_streams/stdin_stdout_stderr.html). The restoring context manager shown below simplifies this pattern::

import sys

# prints in console
print "hello world!"

with restoring('sys.stdout'):
    with open('hello.txt', 'w') as sys.stdout:
        # prints in file
        print "hello world!"

# prints in console again
print "hello world!"

Handle exit context manager (Python)

2014-08-01T08:28:07-07:00

Python recipe 577997 by Giampaolo Rodolà (atexit, contextlib, contextmanager, exit, python, python3, shutdown, sigint, signal, sigterm). Revision 23.

A context manager which properly handles SIGTERM (SystemExit) and SIGINT (KeyboardInterrupt) signals, registering a function which is always guaranteed to be called on interpreter exit. Also, it makes sure to execute previously registered functions as well (if any).

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