pyswitch.sh

#!/bin/sh

py2=$(which python2 2>/dev/null)
py3=$(which python3 2>/dev/null)
py=$(which python 2>/dev/null)

oldcol="\033[31;1m"
newcol="\033[32;1m"
arrowcol="\033[33;1m"

if [ -z "$py2" ]; then
	echo "Python 2 doesn't exist."
	exit 1
elif [ -z "$py3" ]; then
	echo "Python 3 doesn't exist."
	exit 1
elif [ -z "$py" ]; then
	echo "Python doesn't exist."
	exit 1
fi

printf "${oldcol}%s" "$(python --version 2>&1)"

if python --version 2>&1 | grep 'Python 2' > /dev/null; then
	sudo rm "$py"
	sudo ln -s "$py3" "$py"
elif python --version 2>&1 | grep 'Python 3' > /dev/null; then
	sudo rm "$py"
	sudo ln -s "$py2" "$py"
else
	echo "Your python is neither version 2 nor 3, sorry."
	exit 1
fi

printf " ${arrowcol}=> ${newcol}%s\n" "$(python --version 2>&1)"