This is a terminal, made using Bash.
This takes input from the user, with the terminal prompt text being ~$, and stores the command entered by the user in a variable called cmd.
Then, it uses the Bash eval command to a) evaluate the user's input string as a Bash command, and b) make it functional.
#!/bin/bash
clear
while :
do
read -p '~$ ' cmd
if [ "$cmd" = "python" ]; then
python2
elif [ "$cmd" = "exit" ];then
echo exit
break
else
eval "$cmd"
fi
done