run

Run a pex_binary target.

---

To run an executable/script, use ./pants run on a pex_binary target. (See package for more on the pex_binary target.)

$ ./pants run project/app.py

or

$ ./pants run project:app

To pass arguments to the script/executable, use -- at the end of the command, like this:

$ ./pants run project/app.py -- --arg1 arg2

You may only run one target at a time.

The program will have access to the same environment used by the parent ./pants process, so you can set environment variables in the external environment, e.g. FOO=bar ./pants run project/app.py. (Pants will auto-set some values like $PATH).

Tip: check the return code

Pants will propagate the return code from the underlying executable. Run echo $? after the Pants run to see the return code.

Issues finding files?

Run ./pants dependencies --transitive path/to/binary.py to ensure that all the files you need are showing up, including for any resources you intend to use.

Watching the filesystem

If the app that you are running is long lived and safe to restart (including web apps like Django and Flask or other types of servers/services), you can set restartable=True on your pex_binary target to indicate this to Pants. The run goal will then automatically restart the app when its input files change!

On the other hand, if your app is short lived (like a script) and you'd like to re-run it when files change but never interrupt an ongoing run, consider using ./pants --loop run instead. See Goals for more information on --loop.

Debugging

Tip: Using the IntelliJ/PyCharm remote debugger

First, add the following target in some BUILD file (e.g., the one containing your other 3rd-party dependencies):

python_requirement(
  name = "pydevd-pycharm",
  requirements=["pydevd-pycharm==203.5419.8"],  # Or whatever version you choose.
)

You can check this into your repo, for convenience.

Now, use the remote debugger as usual:

1. Start a Python remote debugging session in PyCharm, say on port 5000.
2. Add the following code at the point where you want execution to pause and connect to the debugger:

import pydevd_pycharm
pydevd_pycharm.settrace('localhost', port=5000, stdoutToServer=True, stderrToServer=True)

Run your executable with ./pants run as usual.

Note: The first time you do so you may see some extra dependency resolution work, as pydevd-pycharm has now been added to the binary's dependencies, via inference. If you have dependency inference turned off in your repo, you will have to manually add a temporary explicit dependency in your binary target on the pydevd-pycharm target.