how to set different PYTHONPATH variables for python3 and python2 respectively
I found that there is no way to modify PYTHONPATH
that is only for python2
or only for python3
. I had to use a .pth
file.
What I had to do was:
- make sure directory is created in my home:
$HOME/.local/lib/python${MAJOR_VERSION}.${MINOR_VERSION}/site-packages
- create a
.pth
file in that directory - test that your
.pth
file is work - done
For more info on `.pth. file syntax and how they work please see: python2 docs and python3 docs.
(.pth
files in a nutshell: when your python interpreter starts it will look in certain directories and see the .pth
file, open those files, parse the files, and add those directories to your sys.path
(i.e. the same behavior as PYTHONPATH
) and make any python modules located on those directories available for normal importing.)
You can create a configuration file mymodule.pth
under lib/site-packages
(on Windows) or lib/pythonX.Y/site-packages
(on Unix and Macintosh), then add one line containing the directory to add to python path.
From docs.python2 and docs.python3:
A path configuration file is a file whose name has the form
name.pth
and exists in one of the four directories mentioned above; its contents are additional items (one per line) to be added tosys.path
. Non-existing items are never added tosys.path
, and no check is made that the item refers to a directory rather than a file. No item is added tosys.path
more than once. Blank lines and lines beginning with # are skipped. Lines starting withimport
(followed by space or tab) are executed.
PYTHONPATH
is somewhat of a hack as far as package management is concerned. A "pretty" solution would be to package your library and install it.
This could sound more tricky than it is, so let me show you how it works.
Let us assume your "package" has a single file named wow.py
and you keep it in /home/user/mylib/wow.py
.
Create the file /home/user/mylib/setup.py
with the following content:
from setuptools import setup
setup(name="WowPackage",
packages=["."],
)
That's it, now you can "properly install" your package into the Python distribution of your choice without the need to bother about PYTHONPATH
. As far as "proper installation" is concerned, you have at least three options:
"Really proper". Will copy your code to your python site-packages directory:
$ python setup.py install
"Development". Will only add a link from the python site-packages to
/home/user/mylib
. This means that changes to code in your directory will have effect.$ python setup.py develop
"User". If you do not want to write to the system directories, you can install the package (either "properly" or "in development mode") to
/home/user/.local
directory, where Python will also find them on its own. For that, just add--user
to the command.$ python setup.py install --user $ python setup.py develop --user
To remove a package installed in development mode, do
$ python setup.py develop -u
or
$ python setup.py develop -u --user
To remove a package installed "properly", do
$ pip uninstall WowPackage
If your package is more interesting than a single file (e.g. you have subdirectories and such), just list those in the packages
parameter of the setup
function (you will need to list everything recursively, hence you'll use a helper function for larger libraries). Once you get a hang of it, make sure to read a more detailed manual as well.
In the end, go and contribute your package to PyPI -- it is as simple as calling python setup.py sdist register upload
(you'll need a PyPI username, though).