I am a complete beginner to Python/Django, but I want to dive right in and start experimenting. Thus I was following this guide on installing Python/Django http://devcenter.
I'm running macOS and I'm using pyenv instead of virtualenv. I'm not sure if they behave similarly, but I was having the same problem in which django-admin.py was not found.
After a while I've noticed that I had a warning after installing django:
pyenv: cannot rehash: /Users/msvolenski/.pyenv/shims/.pyenv-shim exists
Once I deleted this file and ran pyenv rehash
it all started working perfectly.
Hope this helps!