PTO

Easy timeouts for Python

PTO is an MIT-licensed library to make it easy to impose time limits on the runtime of a function that doesn't expose that functionality itself. I was inspired by a need to prevent a scheduled job from running too long on a platform where I was paying by the hour. Maybe you just need to wrap a flaky network call. Either way, it's as simple as:

>>> from pto import timeout
>>> @timeout(5)
... def slow_func():
...     while True:
...         pass
...
>>> slow_func()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 2, in slow_func
  File "pto/__init__.py", line 97, in _timeout
    result = f(*args, **kwargs)
  File "<stdin>", line 3, in slow_func
  File "pto/__init__.py", line 89, in handle_timeout
    raise TimedOutException
pto.TimedOutException: u'Timed Out'

Inspiration

I was inspired to do this by Chris Wright's recipe. I liked the recipe, but I got tired of copying and pasting it, and I didn't like that the decorator didn't preserve the signature, docstring, etc.

Caveats

This only works on Unix-like platforms. Sorry, Windows users. I'd love to support Windows, but the secret sauce (signal.alarm from the std lib) doesn't work on Windows.

This isn't really designed to play well with threads, because only the main thread will receive signals in Python. Anyway, if you're using threads, you probably have other ways to handle timeouts.

If you want to put timeouts on static methods or class methods, you need to put the timeout on the method first, and then decorate the wrapped method with @staticmethod or @classmethod. There are examples in test_pto.py.

I am pretty sure that the lib works in Python 2.4, but I don't have an install around to test that. If anybody wants to volunteer to verify the lib on 2.4, please contact me.

Installation

To install PTO, simply:

$ pip install pto

Or, if you absolutely must:

$ easy_install pto

But, you really shouldn't do that.

History

0.0.7 (2013-03-14)

• Enhanced ignores
• Enable setup.py test
• Customize dependencies for Python 3 vs. Python 2
• Add Travis-CI status image to README.rst

0.0.6 (2013-03-13)

• Add unit-testing
• Enable Travis-CI
• Add some more caveats/gotchas to README.rst
• Update sample usage
• Update trove classifiers

0.0.5 (2013-03-13)

• Include proper path for license in MANIFEST.in

0.0.4 (2013-03-13)

• Embed license on PyPI page.

0.0.3 (2013-03-13)

• First version that pip can actually install.

0.0.2 (2013-03-12)

• First draft

0.0.1 (2013-03-11)

• Conception