在 OSX lion/launchd 中，python/serial 坏了

Question

I have a launchd entry that worked with OSX 10.6 but that fails with 10.7. It uses python, and it produces an error whilst trying to import serial . I don't quite understand this, because I've re-downloaded pyserial-2.5 and re-installed it with sudo. (In desperation, I re-installed it for each of the many flavours of python on my machine.) As a test, I can enter python and do import serial without difficulties. Maybe there is a system path that is set up well for an interactive user, that is not set up for launched??

Can anyone suggest how I might diagnose the problem?

Answer 1

The path you are appending:

/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages

is the site-packages directory for a third-party, non-system Python, possibly installed using a python.org installer, and not that of the Apple-supplied system Python 2.7, which would be:

/Library/Python/2.7/site-packages

So most likely you are using the python.org Python to install pyserial but are launching the system Python under launchd . Check your shell PATH ( echo $PATH ), it probably has:

/Library/Frameworks/Python.framework/Versions/2.7/bin

in it. And try which python . If you want to use the python.org Python with your launchd plist, modify it to use an absolute path to the right Python, for instance:

/Library/Frameworks/Python.framework/Versions/2.7/bin/python

If you want to install pyserial with the system supplied Python, you can use an absolute path to it when doing the install:

/usr/bin/python2.7

Answer 2

Some experimentation with python -S showed me that the sys.path was not set up properly, so I solved the issue by

import sys
sys.path.append('/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages')
import serial

which I know is awkward, since it is so specific, but I guess I'll have to live with that, unless or until I can find a way to tell python where to find things, as it is being invoked from launched .

PS to anyone coming here later: the switch to OSX 10.7 (Lion) changed loads of things. Perhaps I had some initialization file somewhere, that I forgot about. If I find that, I'll try it that way, and post a further comment here.