flaskr tutorial; can't import flaskr (initialize database)

I'm new to programming, and tried to work through the flask tutorial. http://flask.pocoo.org/docs/tutorial/

I'm stuck on this part (from the readme on github) when trying to run the app: https://github.com/mitsuhiko/flask/tree/master/examples/flaskr/

Fire up a python shell and run this:

from flaskr import init_db; init_db()

I get this error when I try to run the command in python shell:

Import error: No module named flaskr

And I get this error when I try to run app locally:

sqlite3.OperationalError
OperationalError: unable to open database file

I've been looking for solution for several hours now, but to no avail. Any thoughts on what I could check? Thank you.