Vimrc python37

[eirnym]

Uses Python 3.7 from Python.org if installed (this was overlooked since build 150), credits to @kiryph
Adds checks MacPorts if python from it is used after Homebrew.

[kiryph]

Great idea to improve the macvim/vimrc file itself, so python3 installation from macports, next to https://www.python.org/downloads/mac-osx/, is also used if present.

Add homebrew as well

I think you did not actually add the location of homebrew:

setpythonthreehome=/usr/local/Frameworks/Python.framework/Versions/3.7

This would be a third if-clause.
Homebrew python3 is used by default from macvim. So your PR should be fine.

(I do not like the asymmetry between python2 and python3 configuration: python2-homebrew has to be set, for python3-homebrew nothing; maybe this has something to do that a python2 is pre-installed)

[eirnym]

macOS still doesn't have any Python3 preinstalled and this leads to a different handling of Python versions. Rumors said that macOS 10.14 doesn't have it as well.
So for basic binary installation you'll have no problem to use :py or :pyx commands, but it's required to install Python 3 from any other source if needed.

[kiryph]

By default the pre-installed python2 is used?

[eirnym]

yes, according to strings Vim | grep Python (I use the binary installation from github)

[kiryph]

I also use the binary installation from github. So the results on my machine agree:

❯ strings /Applications/MacVim.app/Contents/MacOS/Vim | grep Python
/usr/local/Frameworks/Python.framework/Versions/3.7/Python
/System/Library/Frameworks/Python.framework/Versions/2.7/Python

It is good to confirm this specifically. Thanks for pointing this method out.
However, I noticed in the past that the exact version has to match, e.g. 3.6.4 instead of 3.6.3.
Do you know a possibility how to figure the exact version number out from the binary?

Order of Used Python Versions

determined how MacVim is built and by the distributed MacVim $VIM/vimrc

Python2:

1. /usr/local/Library/Frameworks/Python.framework/Versions/2.7 (Homebrew)
2. /opt/local/Library/Frameworks/Python.framework/Versions/2.7 (MacPorts)
3. /System/Library/Frameworks/Python.framework/Versions/2.7 (system, configured)

Python3:

1. /usr/local/Library/Frameworks/Python.framework/Versions/3.7 (Homebrew, configured)
2. opt/local/Library/Frameworks/Python.framework/Versions/3.7 (MacPorts)
3. /Library/Frameworks/Python.framework/Versions/3.7 (python.org)

Update Comments

IMHO, the comments in $VIM/vimrc could be updated and made more explicit:

" Python2
" MacVim is configured by default to use the pre-installed python2 version in
" /System/Library/Frameworks/Python.framework/Versions/2.7/Python
" However, following code adjusts the used python2 version if a Homebrew or
" MacPorts python2 installation can be found:

" Python3
" MacVim is configured to use Homebrew python3 installed into
" /usr/local/Frameworks/Python.framework/Versions/3.7/Python
" If this cannot be found, following code tries to find a MacPorts
" or python3 installation from python.org:

Also a comment from https://github.com/macvim-dev/macvim/wiki/Python-2.x-and-Python-3.x
could be added:

" Python2 & Python3
" Common Python distribution doesn't allow to use Python 2.7 and Python 3.7
" at the same time due to Python shared module loading.
" More details and how to built python2, python3 and MacVim yourself
" to achieve this can be found here
" https://github.com/macvim-dev/macvim/wiki/Python-2.x-and-Python-3.x

Finally, the user could be reminded if he has installed python2/3 in a non-default directory, he must
adjust it himself in his vimrc.

Python2 from python.org

For python2, an installation from https://www.python.org/downloads/release/python-2715/
could be also be preferred instead of the pre-installed version. The order would look like

1. /usr/local/Library/Frameworks/Python.framework/Versions/2.7 (Homebrew)
2. /opt/local/Library/Frameworks/Python.framework/Versions/2.7 (MacPorts)
3. /Library/Frameworks/Python.framework/Versions/2.7 (python.org)
4. /System/Library/Frameworks/Python.framework/Versions/2.7 (system, configured)

[eirnym]

@kiryph added comments without paths as they constant and well known for both installations. Also I added a python 2.7 from python.org installation detection. Although, I resigned to add a comment of simulteniuos loading of Python 2 and 3 as it described in :help python page as this is a part of the base Vim as well as adjusting these pats. Nevertheless, you is allowed to specify paths as they're just options.