Installed Virtualenv and activating virtualenv doesn't work

Question

I cloned my Django Project from Github Account and activated the virtualenv using famous command source nameofenv/bin/activate And when I run python manage.py

Answer 1

If you have several python on your machine, for example,python2.7, python3.4, python3.6, it is import to figure out which version the python really reference to, and more over, which version does pip reference to.

The same problem got in my way after I installed the let's encrypt when I run the following command.

(python3 manage.py runserver 0:8000 &)

I inspected the python version and found that python3, python3.4, python3.6, python3.4m were all available.

I just change python3 to python3.6 and solved the problem.

(python3.6 manage.py runserver 0:8000 &)

So, this is probably a version mismatching problem if it is OK for a long time and crashes down suddenly.