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Flask, PyMySQL, and Virtualenvs

Our basic infrastructure would conventionally look like this. (Note that I've used MySQLdb as the Python package; we'll use PyMySQL and cs304dbi.)

Structure of a basic Flask/MySQL app with venv and templates

If one were to have several such apps, the conventional approach would be to make them all separate:

Several basic Flask/MySQL apps with separate virtual environments.
  • This allows them to be completely independent, but
  • doesn't allow for any sharing of Python packages, and
  • requires creating a new venv and re-installing Python packages whenever we want a new project.

Instead, since all our work is similar and related, let's share a single virtual environment:

Several basic Flask/MySQL apps with one, shared virtual environment.

Working on a Project

When we start working on a project (either for the first time or continuing work we did earlier), we do:

cd ~/cs304 
source venv/bin/activate 
cd project
python app.py

Alternatively:

source ~/cs304/venv/bin/activate
cd cs304/project
python app.py

BTW, I strongly suggest that we name the "main" python file app.py. It just makes it a little easier for me and for the graders to figure out which python file we have to run.

Copying a Project

With this new structure, copying a project becomes much easier. For example, to copy hwk3 to hwk4 (this preserves hwk3 for grading purposes while you start working on hwk4), do the following:

cd ~/cs304 
cp -r hwk3 hwk4