No module named flask using virtualenv

Question

I am following these steps to learn flask http://blog.miguelgrinberg.com/post/the-flask-mega-tutorial-part-i-hello-world/page/0#comments

I ran this command to create

Answer 1

I had this same problem on three Raspberry Pi units at the same time; beat my head against the wall trying to fix it for several hours (reinstall flask via pip, apt and aptitude - no joy).

Instead of:

pip install flask

I finally tried:

pip install Flask

Worked like a charm.