Lecture 36

Using Flask

MCS 275 Spring 2021
David Dumas

Lecture 36: Using Flask

Course bulletins:

• Please install Flask, e.g. with

  python3 -m pip install Flask

  in preparation for using it in upcoming assignments.
• Project 4 description likely to be posted tonight.

Today's goal

Build the database and Flask routes for our web apps.

Get a minimal working version of at least one of them running.

Chat app todo

• ✓ HTML mockup
• ✓ Stylesheet
• ✓ (Learn a bit about Flask)
• Database schema & test data
• Python code to generate message view HTML from a database query
• Add form to post a message to HTML
• Create route for new message submission

Vote app todo

Everything from previous list and:

• Second view (chrono vs score)
• Routes for the + and - buttons

Chat DB schema

Table messages has columns:

• id - integer uniquely identifying a message
• sender - name of the sender
• content - message content
• ts - float giving time message received by server in seconds since unix epoch (0:00 Jan 1 1970 UTC)

Generating chat feed

• SELECT query retrieves messages
• Convert each row to a <div> using string formatting.
• Add static parts of the HTML page (header and footer).
• When a Flask route returns a string, Flask assumes it is HTML and delivers it as the response (with HTTP response code 200, and adding necessary headers).