Not working with python version 3.9-dev

[martinosorb]

🐛 Bug

Pytorch lightning fails to import on python 3.9-dev (3.9.12+) due to the use of Version on an inappropriately formatted version string:

File ~/.pyenv/versions/3.9-dev/lib/python3.9/site-packages/pytorch_lightning/utilities/imports.py:90, in <module>
     88 _IS_WINDOWS = platform.system() == "Windows"
     89 _IS_INTERACTIVE = hasattr(sys, "ps1")  # https://stackoverflow.com/a/64523765
---> 90 _PYTHON_GREATER_EQUAL_3_8_0 = Version(platform.python_version()) >= Version("3.8.0")
     91 _TORCH_GREATER_EQUAL_1_8_1 = _compare_version("torch", operator.ge, "1.8.1")
     92 _TORCH_GREATER_EQUAL_1_9 = _compare_version("torch", operator.ge, "1.9.0")

...

InvalidVersion: Invalid version: '3.9.12+'

To Reproduce

import pytorch_lightning on my setup with python 3.9-dev.

Expected behavior

The version check should not be based on platform.python_version(), as this is a string and apparently it's not PEP 440-compliant. There are better ways to get python version in a machine-readable way.

Environment

• CUDA:
  • GPU:
    • NVIDIA GeForce RTX 3070 Laptop GPU
  • available: True
  • version: 11.3
• Packages:
  • numpy: 1.21.6
  • pyTorch_debug: False
  • pyTorch_version: 1.12.0.dev20220517+cu113
  • tqdm: 4.64.0
  • pytorch-lightning 1.6.4
• System:
  • OS: Linux
  • architecture:
    • 64bit
    • ELF
  • processor: x86_64
  • python: 3.9.12+
  • version: fixed clip grad warning #42-Ubuntu SMP Thu Jun 9 23:42:32 UTC 2022
    of torch.__config__.show():

[awaelchli]

Hello

There are better ways to get python version in a machine-readable way.

What is your suggestion concretely?

The only other way I know is through sys.version_info. Could you check on your system with python 3.9-dev that the comparison sys.version_info >= (3, 8) holds true? If so, we can update it to use that.

[awaelchli]

Would you be open to submit a PR with a fix?

[martinosorb]

The correct way seems to be (sys.version_info.major, sys.version_info.minor) >= (3, 8) (per comments here).

Will try it out.

[martinosorb]

See PR. I could only run standalone tests.