# Open Source PyMol Conda Package: UnsatisfiableError

I'm having an issue installing the open-source version of Pymol using Anaconda on Windows. I have Python3.8.3 installed and when I try add the package with Conda using conda install -c tpeulen pymol-open-source, I get the error

UnsatisfiableError: The following specifications were found
to be incompatible with the existing python installation in your environment:

Specifications:

- pymol-open-source -> python[version='>=3.7,<3.8.0a0']



Okay so it can't do python3.8? Not a problem, I'll just make a Python3.7 virtual environment conda create -n "py37" python=3.7.9. Except, for some reason this still returns an error.

UnsatisfiableError: The following specifications were found
to be incompatible with the existing python installation in your environment:

Specifications:

- pymol-open-source -> python[version='>=2.7,<2.8.0a0|>=3.6,<3.7.0a0|>=3.8,<3.9.0a0|>=3.5,<3.6.0a0']



This claims that Python3.8 should work and the only version that doesn't work is 3.7! So, as a last attempt I tried switching to Python 3.6.12 and sure enough I got another error:

UnsatisfiableError: The following specifications were found
to be incompatible with the existing python installation in your environment:

Specifications:

- pymol-open-source -> python[version='>=3.7,<3.8.0a0']



This says only 3.7 will work, but that is clearly not the case. Am I using conda wrong here or is there some issue with this package? How can I get the open-source PyMol installed properly?

Note: There is Incentive PyMol released by Schrodinger, which I could successfully install through conda, but this is only a trial version. I would like to use the free version if possible.

• +1. I'm not sure which software tag is the most appropriate, but I've added software-assistance for now! – Nike Dattani Oct 13 at 19:50
• Ah, conda. A solution to a problem that was solved ~two decades ago by linux package managers, only with the joys of DLL dependency hell :D – Susi Lehtola Oct 15 at 23:35

If you're using Linux its better if you install such packages using the apt-get method.

apt-get install pymol

I've encountered a similar error while installing MatPlotLib through conda.

I was able to find a workaround to get open source PyMol installed on Windows. Christoph Gohlke at the University of California has a large library of precompiled Python wheel files of various scientific packages, including PyMol. I was able to find a version for Python3.8 on Windows pymol‑2.5.0a0‑cp38‑cp38‑win_amd64.whl and after downloading this file, I was able to install PyMol using pip python -m pip install pymol‑2.5.0a0‑cp38‑cp38‑win_amd64.whl.
As mentioned on the PyMol wiki, I also had to pip install the pyqt5 package to get the graphical window working. I'm still puzzled why conda didn't work, but at least it's possible to access this program on Windows.