Default to python 3.x on linux

#install the centos7 repository
sudo yum -y install https://centos7.iuscommunity.org/ius-release.rpm
#install python3.6
sudo yum -y install python36u
# install pip3 for python 3.x (since pip is for python 2.x)
sudo yum -y install python36u-pip
# it shows the default python 2.x
python -V
# this is how you run the python 3.x but it is inconvenient
python3.6 -V
# so set alias
# when we run python the OS will not autotranslate that the alias value python3.6
alias python=python3.6
alias pip=pip3.6
# make these alias changes permanent
source ~/.bashrc
# install virtualenv
pip install virtualenv
# how to create a virtual environment for python3? 
# virtualenv <name of the virtual environment>