When using two version of the python (2 and 3) on windows 10 and you need to make one of the versions "main" version. By main version I mean when you call "python" in cmd your main version will open

python_master.sh

#!/bin/bash

#python2 path
py2=v2/v.txt
#C:/Python27/python.exe 
#python3 path
py3=v3/v.txt
#C:/Users/vojislav/AppData/Local/Programs/Python/Python38-32/python.exe

VERSION=$1
echo python master change the python version for python.exe
#echo $VERSION
#if no parameter ask for it
if [ -z $VERSION ]
then
	echo which version you want to be main 2 or 3
	read VERSION
	echo you chose version $VERSION
else	
	echo you chose version $VERSION
fi

if [[ $VERSION -ne '2' ]] && [[ $VERSION -ne '3' ]]
then
	echo wrong verson
	exit 1
fi

#find current main version
if [ -f "$py2" ]
then
    echo "python 2 is main"
elif [ -f "$py3" ]
then
    echo "python 3 is main"
else
	echo there is a problem with versions
	exit 1
fi

#change verson
#version 2 main
if [[ $VERSION -eq '2' ]] && [[ -f "$py3" ]]
then
	mv v3/v.txt v3/v3.txt
	mv v2/v2.txt v2/v.txt
elif [[ $VERSION -eq '3' ]] && [[ -f "$py2" ]]
then
	mv v2/v.txt v2/v2.txt
	mv v3/v3.txt v3/v.txt
else
	echo version $VERSION is already main
fi
	#statements
#version 3 main