.python-version file is a plain text file used by tools like pyenv to automatically define the Python version for a specific project directory. It ensures consistent environments across development, testing, and deployment, commonly identifying the desired version for platforms like Heroku. For more details, visit Heroku Dev Center Heroku Dev Center Specifying a Python Version - Heroku Dev Center
python --version # OR python -V
Prevents "it works on my machine" errors by forcing the same Python version across different developers' environments . .python version
Different version managers interpret the content slightly differently: .python version