In modern development, different projects often require different Python versions. For example, an older legacy app might need , while a new data science project requires Python 3.12 . Managing these manually by changing global paths is error-prone. Tools like pyenv solve this by looking for a .python-version file. How the .python-version File Works
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Tools like Heroku or Render read this file during deployment to install the correct runtime automatically . .python version
To manage multiple Python versions on your system: Python 3