CODEWITHSUNDEEP
pythonenvironment-variablesosx-mountain-lionenthoughtcanopy
AlexNoir
AlexNoir

Reputation: 789

Enthought Canopy: Where do os.environ variables come from?

I have the following problem. I wanted to use the matplotlib package animation to save an mp4 video file. The save function has a dependency for generating the mp4 file, the ffmpeg external library. So I installed ffmpeg on a Mac osx 10.8 via Macports, and it got installed in /opt/local/bin .

But now, running the script in canopy, the interpreter (ipython shell) can not see ffmpeg. I added the path to my .bash_profile, and I can run the program at my terminal, but when I type os.environ['PATH'] the actual PATH of my shell was not added, and /opt/local/bin is not there. If I try to run the script, I get this error:

/Users/alejandrodelacallenegro/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-      packages/matplotlib/animation.py:695: UserWarning: MovieWriter ffmpeg unavailable
warnings.warn("MovieWriter %s unavailable" % writer)

Any ideas to fix the problem? What I have to do to change an environmental variable that python sees at startup? Did anyone have the same problem?
Thanks.

Upvotes: 2

Views: 2788

Answers (1)

abarnert
abarnert

Reputation: 365945

The problem here has nothing to do with Enthought; it's that OS X doesn't run bash when you launch things from Finder, LaunchDaemons, etc., and therefore doesn't access your .bash_profile. Instead, it runs them from launchd.

If you want to add some environment variables to affect anything run by launchd for the current user, that's easy:

launchctl setenv PATH $PATH:/opt/local/bin

If you want this to happen every time you log in, if you create a file ~/.launchd.conf, the subcommands in that file will be run through launchctl every time launchd starts (which is the first step in logging in a new user session).

If you want it to be system-wide, rather than just for your user, you can sudo launchctl and/or create/edit /etc/launchd.conf. However, you almost certainly don't want to change the environment used by root services, etc., unless you really know what you're doing.

If it helps: Using launchctl manually, editing ~/.launchd.conf, and editing /etc/launchd.conf are roughly equivalent to export, ~/.bash_profile, and /etc/profile (except of course that they affect launchd rather than bash/sh).

See the launchctl(1) man page for details, or just type launchctl to start an interactive session and use the built-in help. (The pages launchd(8) and launchd.conf(5) also have useful info.)

You can also use the deprecated environment.plist file to affect even things that aren't run by launchd, but… that's deprecated, and there really isn't anything for it to affect that you care about, except in (much) older versions of OS X.

People coming from other Unix systems are often caught out by this. Most file managers ask the shell to run programs for them; Finder.app (and the command-line tool open, and the AppleScript environment, and so on) ask launchd to do it. Plus, on most X11 systems, if you look up the process tree from your file manager, it was ultimately launched by a user shell too, whereas on OS X, Finder.app was launched by launchd, which was launched by the system-wide launchd; no shell in sight.

This also means that other shell-specific stuff like changing resource limits or default umask won't affect programs started outside the shell on a Mac. launchctl is again the answer.

Upvotes: 7

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