Pyquitter overview

So, you've got a program that you're working on, and you're tired of hitting Ctrl-C, Up, Enter. You'd like it to just restart every time you make a change. Here's how Pyquitter helps you solve this problem:

1. Early in your program startup, you instantiate pyquitter.detector.ChangeDetector with a 0-arg callable (one that quits your program).

2. In addition, you set up a timer to call yourChangeDetector.poll() every few seconds. If any of your imported modules have changed, the callable you passed in earlier will be called.

3. Your callable quits your program. (sys.exit(), or if using Twisted, reactor.stop())

4. A parent process keeps restarting your program in a loop. You can use the included bin/looper if it suits your needs.

Installation

python setup.py install

This installs the module pyquitter as well as the binaries looper and looper-stop.

Pyquitter is also available on PyPI http://pypi.python.org/pypi/Pyquitter and you can install it with pip:

pip install Pyquitter

Sample use

This example uses Twisted, but there's nothing Twisted-specific in Pyquitter.

# demo.py

import sys
from twisted.python import log
log.startLogging(sys.stdout)

from twisted.internet import task
from twisted.internet import reactor
from pyquitter.detector import ChangeDetector

stopper = ChangeDetector(
    lambda: reactor.callWhenRunning(reactor.stop),
    logCallable=log.msg)
    # logCallable is optional; if not passed, it uses print.

looping = task.LoopingCall(stopper.poll)
looping.start(1.0, now=True) # check every 1 sec

reactor.run()

Run the above program with looper, which will restart it every time it quits:

looper python demo.py

or on Windows:

C:\Python27\Scripts\looper C:\Python27\python demo.py

(Note that in the normal cmd shell, the above command actually runs looper.bat.)

If you modify demo.py or any module it has imported, you'll see the program restart. If a module is modified but there are syntax errors, the callable passed to ChangeDetector will not be called until the syntax errors are fixed.

Watching for changes to non-module files

After stopper = in the above example:

stopper.watchNonModuleFile('/home/me/my_settings.py')
stopper.watchNonModuleFile('/home/me/blob')

Note that because /home/me/my_settings.py ends with '.py', the file will be checked for syntax errors using Python's compile function. As with module files, if there are syntax errors, callable will not be called until the errors are fixed.

To stop watching a non-module file:

stopper.forgetNonModuleFile('/home/me/my_settings.py')

Running the tests

Install Twisted, then trial pyquitter.

Wishlist

• Detect changes to modules outside of the process. Feed a list of files to some parent process that monitors the modules for the often-restarting child. This would fix a race condition where a module is changed before ChangeDetector takes a look at it.

• Rewrite the tests; don't spawn child pythons.

• Document optional use of Pyflakes (see the source for now).

Contributing

Patches and pull requests are welcome.

This coding standard applies: http://ludios.org/coding-standard/