I am using OSX and I have pip installed for both Python3.5 and Python2.7. I know I can run the command pip2 to use Python2 and when I use the command pip3
Can't you alias pip='pip3' in your ~/.bash_profile?
In Terminal, run nano ~/.bash_profile, then add a line to the end that reads alias pip='pip3'. This is safe; it won't affect system processes, only your terminal.