There is an issue with downloading and installing Python 3.6. Unchecking pip in the installation prevents the issue. So pip is not given in every installation.
How did you install Python, and are you using a virtual environment?
As you specifically mentioned Python 3.6, and you have not marked this as answered I will make a guess that you might have installed it using sudo add-apt-repository ppa:jonathonf/python-3.6, as this is a common way to install Python 3.6 on a Unix OS that doesn't have a native 3.6 package. If this is the case the correct way to install pip is as follows ....
Step 1) Make a Virtual Environment with Python 3.6 ...
Yes, Python3.6 installs PIP but it is unreachable as it is installed. There is no code which will invoke it as it is! I have been at it for more than a week and I read every single advice given, without success!
Finally, I tested going to the pip directory and upgrading the installed version:
That command created a PIP which now works properly from any location on my FreeBSD server!
Clearly, the tools installed simply do not work, as installed with Python3.6. The only way to run them is to invoke Python and the desired python files as you can see in the command issued. Once the update is called, however, the new PIP works globally without having to invoke Python3.6...