How do I properly install PyGObject? (OSX)

Question

I want to run existing simple examples and write some simple code using GStreamer - specifically, using its Python bindings. I want to install the packages etc to enable that.

Here's an example.

http://brettviren.github.io/pygst-tutorial-org/pygst-tutorial.html

import gi
gi.require_version('Gst', '1.0')
from gi.repository import Gst
Gst.init(None)
# ...
my_playbin = Gst.ElementFactory.make("playbin", None)
assert my_playbin
print my_playbin

I can't get PyGObject to work, so I'm stuck right at import gi and can't make any progress beyond the first line.

The platform is MacOS 10.12.6, and Python 3.6.5.

computer:Desktop me$ python3
Python 3.6.5 (v3.6.5:f59c0932b4, Mar 28 2018, 05:52:31) 
[GCC 4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.57)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import gi
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'gi'
>>> 

Okay, let's RTFM.

https://pygobject.readthedocs.io/en/latest/getting_started.html#macosx-getting-started

Seems pretty simple and this should get PyGObject installed, right?

I've already got Homebrew installed, but let's just do it again to be sure.

computer:Desktop me$ /usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

==> This script will install:
/usr/local/bin/brew

[Snip for brevity]

==> Installation successful!

==> Next steps:
- Run `brew help` to get started
- Further documentation: 
    https://docs.brew.sh

computer:Desktop me$ 

OK, now let's install pygobject3 and gtk+3

computer:Desktop me$ brew install pygobject3 gtk+3
Updating Homebrew...
Warning: pygobject3 3.32.1 is already installed and up-to-date
To reinstall 3.32.1, run `brew reinstall pygobject3`
Warning: gtk+3 3.24.8 is already installed and up-to-date
To reinstall 3.24.8, run `brew reinstall gtk+3`
computer:Desktop me$

Now let's try Python again:

computer:Desktop me$ python3
Python 3.6.5 (v3.6.5:f59c0932b4, Mar 28 2018, 05:52:31) 
[GCC 4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.57)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import gi
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'gi'
>>> 

So we've followed the instructions and we're still right where we started with no functionality.

Also tried various --with-python3 and --without-python options during the brew install.

computer:Desktop me$ brew install pygobject3 --with-python3 --without-python
    Updating Homebrew...

    [SNIP FOR BREVITY]

    Error: invalid option: --with-python3

All of these options are invalid options, despite being mentioned in various internet threads.

computer:Desktop me$ brew install pygobject3 --with-python@2 gtk+3
Updating Homebrew...
==> Auto-updated Homebrew!
Updated 1 tap (homebrew/cask).
No changes to formulae.

[SNIP FOR BREVITY] 

Error: invalid option: --with-python@2

Can somebody tell me what I'm missing please?

Answer 1

I know this answer is a bit late, but I figured out why it isn't working and a workaround for those who run into it in the future.

Homebrew will install pygobject3 by symlinking it in from a package install directory, which means that pygobject3 is only accessible from the python binaries installed by homebrew. If I used the python executable at /usr/local/bin/python3 , the install location of brew install python , pygobject3 imports just fine.

Obviously, that's suboptimal, and we want to transfer pygobject3 to our preferred installation of python.

I did it like so:

$ cd /usr/local/Cellar/pygobject3/3.34.0/lib/python3.7/site-packages/
$ sudo cp -rf * /usr/local/anaconda3/lib/python3.7/site-packages/

I can now import and use gi:

(base) 2l4@mac105220:/usr/local/anaconda3/lib/python3.7/ > python
Python 3.7.3 (default, Mar 27 2019, 16:54:48)
[Clang 4.0.1 (tags/RELEASE_401/final)] :: Anaconda, Inc. on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from gi.repository import GLib
>>> loop = GLib.MainLoop()
>>> loop.run()