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

This problem can also arise if the port is not available. Try running on different port.

Answer 2

Make sure your virtualenv is activated. Then You check on the PYTHONPATH of that virtualenv. Is there a flask package (folder) installed in that directory.

If you unsure whether you have installed flask, just run the following command to see all the packages you have installed pip list or pip show flask. Do you see flask there? If not you can run pip install flask

Answer 3

If nothing else helps, check that in your code it is:

from flask import Flask

I've tried many things before I've noticed my mistake. I had this in my code:

from Flask import Flask

When I have changed capitalized letter for the module name, i.e. flask then everything worked.

Answer 4

Activate your virtual environment first with

source bin/activate envName

Then try to run your command again

Answer 5

I am running Python on windows 7. I had same problem No module named flask.

I tried reinstalling python, venv but it did not work.

Finally i run it like this

1. Install venv the usual way
2. go to scripts directory and activate
3. C:\Python34\microb>c:\Python34\microb\fla\scripts\python run.py
4. here microb is my project and fla is venv

Answer 6

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.