pypi i hupper


in-process file monitor / reloader for reloading your code automatically during development

by Pylons

1.10.3 (see all)License:MIT
pypi i hupper



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.. image:: :target: :alt: Documentation Status

hupper is an integrated process monitor that will track changes to any imported Python files in sys.modules as well as custom paths. When files are changed the process is restarted.

Command-line Usage

Hupper can load any Python code similar to python -m <module> by using the hupper -m <module> program.

.. code-block:: console

$ hupper -m myapp Starting monitor for PID 23982.

API Usage

Start by defining an entry point for your process. This must be an importable path in string format. For example, myapp.scripts.serve.main.

.. code-block:: python

# myapp/scripts/

import sys
import hupper
import waitress

def wsgi_app(environ, start_response):
    start_response('200 OK', [('Content-Type', 'text/plain')])
    yield b'hello'

def main(args=sys.argv[1:]):
    if '--reload' in args:
        # start_reloader will only return in a monitored subprocess
        reloader = hupper.start_reloader('myapp.scripts.serve.main')

        # monitor an extra file



hupper is inspired by initial work done by Carl J Meyer and David Glick during a Pycon sprint and is built to be a more robust and generic version of Ian Bicking's excellent PasteScript paste serve --reload and Pyramid's pserve --reload.

1.10.3 (2021-05-13)

  • Support Python 3.8 and 3.9.

  • Fix an issue with bare .pyc files in the source folder causing unhandled exceptions. See

  • Fix issues with using the Watchman file monitor on versions newer than Watchman 4.9.0. This fix modifies hupper to use Watchman's watch-project capabilities which also support reading the .watchmanconfig file to control certain properties of the monitoring. See

1.10.2 (2020-03-02)

1.10.1 (2020-02-18)

  • Performance improvements when using Watchman.

1.10 (2020-02-18)

  • Handle a SIGTERM signal by forwarding it to the child process and gracefully waiting for it to exit. This should enable using hupper from within docker containers and other systems that want to control the reloader process.

    Previously the SIGTERM would shutdown hupper immediately, stranding the worker and relying on it to shutdown on its own.


  • Avoid acquiring locks in the reloader process's signal handlers. See

  • Fix deprecation warnings caused by using the imp module on newer versions of Python. See

1.9.1 (2019-11-12)

1.9 (2019-10-14)

1.8.1 (2019-06-12)

  • Do not show the KeyboardInterrupt stacktrace when killing hupper while waiting for a reload.

1.8 (2019-06-11)

1.7 (2019-06-04)

1.6.1 (2019-03-11)

1.6 (2019-03-06)

  • On systems that support SIGKILL and SIGTERM (not Windows), hupper will now send a SIGKILL to the worker process as a last resort. Normally, a SIGINT (Ctrl-C) or SIGTERM (on reload) will kill the worker. If, within shutdown_interval seconds, the worker doesn't exit, it will receive a SIGKILL. See

  • Support a logger argument to hupper.start_reloader to override the default logger that outputs messages to sys.stderr. See

1.5 (2019-02-16)

  • Add support for ignoring custom patterns via the new ignore_files option on hupper.start_reloader. The hupper cli also supports ignoring files via the -x option. See

1.4.2 (2018-11-26)

  • Fix a bug prompting the "ignoring corrupted payload from watchman" message and placing the file monitor in an unrecoverable state when a change triggered a watchman message > 4096 bytes. See

1.4.1 (2018-11-11)

1.4 (2018-10-26)

  • Ignore changes to any system / installed files. This includes mostly changes to any files in the stdlib and site-packages. Anything that is installed in editable mode or not installed at all will still be monitored. This drastically reduces the number of files that hupper needs to monitor. See

1.3.1 (2018-10-05)

  • Support Python 3.7.

  • Avoid a restart-loop if the app is failing to restart on certain systems. There was a race where hupper failed to detect that the app was crashing and thus fell into its restart logic when the user manually triggers an immediate reload. See

  • Ignore corrupted packets coming from watchman that occur in semi-random scenarios. See

1.3 (2018-05-21)

1.2 (2018-05-01)

  • Track only Python source files. Previously hupper would track all pyc and py files. Now, if a pyc file is found then the equivalent source file is searched and, if found, the pyc file is ignored. See

  • Allow overriding the default monitor lookup by specifying the HUPPER_DEFAULT_MONITOR environment variable as a Python dotted-path to a monitor factory. For example, HUPPER_DEFAULT_MONITOR=hupper.polling.PollingFileMonitor. See

  • Backward-incompatible changes to the hupper.interfaces.IFileMonitorFactory API to pass arbitrary kwargs to the factory. See

1.1 (2018-03-29)

1.0 (2017-05-18)

  • Copy sys.path to the worker process and ensure hupper is on the PYTHONPATH so that the subprocess can import it to start the worker. This fixes an issue with how zc.buildout injects dependencies into a process which is done entirely by sys.path manipulation. See

0.5 (2017-05-10)

  • On non-windows systems ensure an exec occurs so that the worker does not share the same process space as the reloader causing certain code that is imported in both to not ever be reloaded. Under the hood this was a significant rewrite to use subprocess instead of multiprocessing. See

0.4.4 (2017-03-10)

0.4.3 (2017-03-07)

0.4.2 (2017-01-24)

0.4.1 (2017-01-03)

  • Handle errors that may occur when using watchdog to observe non-existent folders.

0.4.0 (2017-01-02)

0.3.6 (2016-12-18)

  • Read the traceback for unknown files prior to crashing. If an import crashes due to a module-scope exception the file that caused the crash would not be tracked but this should help.

0.3.5 (2016-12-17)

  • Attempt to send imported paths to the monitor process before crashing to avoid cases where the master is waiting for changes in files that it never started monitoring.

0.3.4 (2016-11-21)

  • Add support for globbing using the stdlib glob module. On Python 3.5+ this allows recursive globs using **. Prior to this, the globbing is more limited.

0.3.3 (2016-11-19)

  • Fixed a runtime failure on Windows 32-bit systems.

0.3.2 (2016-11-15)

  • Support triggering reloads via SIGHUP when hupper detected a crash and is waiting for a file to change.

  • Setup the reloader proxy prior to importing the worker's module. This should allow some work to be done at module-scope instead of in the callable.

0.3.1 (2016-11-06)

  • Fix package long description on PyPI.

  • Ensure that the stdin file handle is inheritable incase the "spawn" variant of multiprocessing is enabled.

0.3 (2016-11-06)

  • Disable bytecode compiling of files imported by the worker process. This should not be necessary when developing and it was causing the process to restart twice on Windows due to how it handles pyc timestamps.

  • Fix hupper's support for forwarding stdin to the worker processes on Python < 3.5 on Windows.

  • Fix some possible file descriptor leakage.

  • Simplify the hupper.interfaces.IFileMonitor interface by internalizing some of the hupper-specific integrations. They can now focus on just looking for changes.

  • Add the hupper.interfaces.IFileMonitorFactory interface to improve the documentation for the callback argument required by hupper.interfaces.IFileMonitor.

0.2 (2016-10-26)

  • Windows support!

  • Added support for watchdog <>_ if it's installed to do inotify-style file monitoring. This is an optional dependency and hupper will fallback to using polling if it's not available.

0.1 (2016-10-21)

  • Initial release.
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