“python_requires” should be set with “>=3.5”, as fklearn 2.0.0 is not compatible with all Python versions.

[PyVCEChecker]

Currently, the keyword argument python_requires of setup() is not set, and thus it is assumed that this distribution is compatible with all Python versions.
However, I found it is not compatible with Python 2. My local Python version is 2.7, and I encounter the following error when executing “pip install fklearn”

Collecting fklearn
  Downloading https://files.pythonhosted.org/packages/1a/aa/b1af28f1d63958e50e82a64f69e5c9cf250b717cdf4a115a82fbc028094e/fklearn-2.0.0.tar.gz (60kB)
     |████████████████████████████████| 61kB 
…
Collecting pandas<2,>=0.24.1
  Downloading https://files.pythonhosted.org/packages/61/57/6c233cc63597c6aa6337e717bdeabf791e8b618e9c893922a223e4e41cf4/pandas-0.24.2-cp27-cp27m-win_amd64.whl (8.3MB)
     |████████████████████████████████| 8.3MB 393kB/s
ERROR: Could not find a version that satisfies the requirement scikit-learn<0.24.0,>=0.21.2 (from fklearn) (from versions: 0.9, 0.10, 0.11, 0.12, 0.12.1, 0.13, 0.13.1, 0.14, 0.14.1, 0.15.0b1, 0.15.0b2, 0.15.0, 0.15.1, 0.15.2, 0.16b1, 0.16.0, 0.16.1, 0.17b1, 0.17, 0.17.1, 0.18rc2, 0.18, 0.18.1, 0.18.2, 0.19b2, 0.19.0, 0.19.1, 0.19.2, 0.20rc1, 0.20.0, 0.20.1, 0.20.2, 0.20.3, 0.20.4, 0.21rc2)
ERROR: No matching distribution found for scikit-learn<0.24.0,>=0.21.2 (from fklearn)

Dependencies of this distribution are listed as follows:

joblib>=0.13.2,<2
numpy>=1.16.4,<2
pandas>=0.24.1,<2
scikit-learn>=0.21.2,<0.24.0
statsmodels>=0.9.0,<1
toolz>=0.9.0,<1

I found that scikit-learn>=0.21.2,<0.24.0 requires Python>=3.5, which results in installation failure of fklearn in Python 2.7.

Way to fix:
modify setup() in setup.py, add python_requires keyword argument:

setup(…
     python_requires=">=3.5",
     …)

Thanks for your attention.
Best regrads,
PyVCEchecker

[Erick G. Islas-Osuna]

I think that I saw something similar but with a python requirement of >=3.6.2 but I'm not sure about the specific package with the issue.

Thank you for revealing this issue.

[PyVCEChecker]

>=3.6.2 is right. The code used the syntax feature variable annotations, and the feature is only compatible with Python 3.6 and above.

[Erick G. Islas-Osuna]

Just in case, in this page you can find that restriction, however, I've already created a PR with the python_requires parameter to avoid problems like the one you reported.