batch file – How Should I Set Default Python Version In Windows?

batch file – How Should I Set Default Python Version In Windows?

This is if you have both the versions installed.

Go to This PCRight-clickClick on PropertiesAdvanced System Settings.

You will see the System Properties. From here navigate to the Advanced Tab -> Click on Environment Variables.

You will see a top half for the user variables and the bottom half for System variables.

Check the System Variables and double-click on the Path (to edit the Path).

Check for the path of Python(which you wish to run i.e. Python 2.x or 3.x) and move it to the top of the Path list.

Restart the Command Prompt, and now when you check the version of Python, it should correctly display the required version.

The Python installer installs Python Launcher for Windows. This program (py.exe) is associated with the Python file extensions and looks for a shebang comment to specify the python version to run. This allows many versions of Python to co-exist and allows Python scripts to explicitly specify which version to use, if desired. If it is not specified, the default is to use the latest Python version for the current architecture (x86 or x64). This default can be customized through a py.ini file or PY_PYTHON environment variable. See the docs for more details.

Newer versions of Python update the launcher. The latest version has a py -0 option to list the installed Pythons and indicate the current default.

Heres how to check if the launcher is registered correctly from the console:

C:>assoc .py
.py=Python.File

C:>ftype Python.File
Python.File=C:Windowspy.exe %1 %*

Above, .py files are associated with the Python.File type. The command line for Python.File is the Python Launcher, which is installed in the Windows directory since it is always in the PATH.

For the association to work, run scripts from the command line with script.py, not python script.py, otherwise python will be run instead of py. If fact its best to remove Python directories from the PATH, so python wont run anything and enforce using py.

py.exe can also be run with switches to force a Python version:

py -3 script.py       # select latest Python 3.X version to be used.
py -3.6 script.py     # select version 3.6 specifically.
py -3.9-32 script.py  # select version 3.9 32-bit specifically.
py -0                 # list installed Python versions (latest PyLauncher).

Additionally, add .py;.pyw;.pyc;.pyo to the PATHEXT environment variable and then the command line can just be script with no extension.

batch file – How Should I Set Default Python Version In Windows?

Running py command will tell you what version you have running. If you currently running 3.x and you need to switch to 2.x, you will need to use switch -2

py -2

If you need to switch from python 2.x to python 3.x you will have to use -3 switch

py -3

If you would like to have Python 3.x as a default version, then you will need to create environment variable PY_PYTHON and set its value to 3.

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