Question

I’m trying to follow this guide.
I made virtualenv and installed flask in it:

Requirement already satisfied (use --upgrade to upgrade): Flask in     /usr/local/lib/python2.7/dist-packages
Requirement already satisfied (use --upgrade to upgrade): Werkzeug>=0.7 in   /usr/local/lib/python2.7/dist-packages (from Flask)
Requirement already satisfied (use --upgrade to upgrade): Jinja2>=2.4 in /usr/local/lib/python2.7/dist-packages (from Flask)

After pip freeze > requirements.txt the file contains only:

argparse==1.2.1
distribute==0.6.28
wsgiref==0.1.2

And there is no Flask package. I’m trying to run simple example and got:

ImportError: No module named flask

How to install the package properly?

Answer 1

You need to run pip freeze > reuirements.txt inside your virtualenv. Thus, make sure that your virtualenv was activated correctly. As the Heroku documentation is mostly written from Linux point of view, this may be a little tricky especially on Windows (see a related question):

• Windows command-prompt activation is done using venv\Scripts\activate.bat
• If you are using Windows PowerShell, you need to run venv\Scripts\activate.ps1 instead.

Note that you need to activate virtualenv for sudo as well. Example:

sudo bash
source venv/bin/activate
pip install Flask

However one of the points in virtualenv is that you don’t need sudo. Thus, you could simply omit using sudo and simply just run:

source venv/bin/activate
pip install Flask