Fix Python – Unable to set default python version to python3 in ubuntu

I was trying to set default python version to python3 in Ubuntu 16.04. By default it is python2 (2.7). I followed below steps :
update-alternatives –remove python /usr/bin/python2
update-alternatives –install /usr/bin/python python /usr/bin/python3

but I’m getting the following error for the second statement,
rejeesh@rejeesh-Vostro-1015:~$ upda….