Hi, I'm trying to set up pants for a mono repo. The apps are written python and using the flask framework. I have a directory called

apps

and for now a single app in a subdirectory

sample

in this a

app.py

When executing

./pants run apps/sample/app.py

pants. build as expected but, I'm not able to run flask in debug mode.

if __name__ == "__main__":
   app.run(host='localhost', port=7002, debug=True)

Then, I get the following error message:

No module named apps.__main__; 'apps' is a package and cannot be directly executed

It runs without errors when:

if __name__ == "__main__":
   app.run(host='localhost', port=7002)

I've tried googling for this issue, but with no luck. Hence now reaching out. It would be nice not having to

ctr-c

and re-run whenever changes are made to the app when developing. Hope to hear from you! BR Alex

Hello Alex, welcome! Good find and pardon if this was difficult to figure out what the issues was. Indeed, it's an issue with Flask's file watcher not playing nicely with Pex for some reason. I opened https://github.com/pantsbuild/pex/issues/1172 just now to track this FYI you may be able to use

debug=True, use_reloader=False

to still get debug benefits, but you unfortunately wouldn't get the rewatcher Would you have an interest in trying out #1172? We're happy to help, it'd be the quickest way to get the fix in sooner Also let us know if we can help with anything else with Pants or if you have feedback!

related: https://github.com/pantsbuild/pants/issues/9462 … we’re planning to work on this general problem soon.

@echoing-nightfall-72095 I've updated the issue Eric filed above - but this is a generic problem with Flask and zipapps - Pex happens to create a zipapp; so Pex doesn't work with Flask. I'll do a bit more work on that issue to help show a workaround that Pex gives you over and above what a zipapp can do. Pants should probably just be creating Pexes with that workaround or an option to do so on pex_binary targets.

Awesome @enough-analyst-54434, then we will go with pants as build tool. It is a very nice tool, but the developer experience will be poor without hot-reloading. Yes @hundreds-father-404 I would like to try out #1172 😄

The Pex 2.1.25 release should happen early next week. The next Pants release to use it will likely be the weekly Friday dev release on 1/22.