Another fun and exciting project: I built a full-stack web app with Bootstrap UI, Flask back-end, and SQLite3 database.
First, you will need to get an API key from IEX (free account registration), which lets you download stock quotes via their API (application programming interface) using URLs like https://cloud.iexapis.com/stable/stock/nflx/quote?token=API_KEY
With the API, run the following within a CS50 IDE's terminal: $ export API_KEY=value (value is your acquired personal API KEY)
Start Flask’s built-in web server: $ flask run
- App Features: register, quote, buy, index, sell, history
- most of html templates (lots of Jinja dynamic content generation) and their UIs
- application.py (lots of routing, logics, and Sqlite3 QUERIES)
- Design an
orderstable to keep track of all stock transactions by all users. It is stored in finance.db
Some of my own notes, while watching Week9 lecture video
Flask app file structure: • application.py • requirements.txt • static/ • templates/
MODEL-VIEW-CONTROLLER (MVC) design pattern - model=SQL(..) the database, - view=what user sees, templates,
-
controller=application.py, the logics that connect M-V, plus routing
-
jinja: Used in HTML templates: {{ var }} , {% block x %} {% endblock %}.
Make use of TEMPLATES: factor out a COMMON layout.html
- {% block body %} {% endblock %}
- in index.html, about.html, etc.: {% extends "layout.html" %} {% block body %} the content {% endblock %}
SENDING emails with Flask:
Privacy concern: In dev environment: store personal info in virtual environment variables (export username=..., and later retrieve via os.getenv("USERNAME"))
- Session: basically, servers plants cookie (i.e. a saved state, a file, a large number) on your device, to help them remember your identity.
- How it works? BROWSER (if have a cookie) sends cookie along with GET requests, and SERVER: validates, then skip login during same sesson, server personal data, etc.
- ENTER Incognito mode: not employing cookies.
Callback: a function that will eventually be called, when it has an answer for you.
An AJAX call: sends additional HTTP request to server (for chat messages, autocomplete, etc.). So WHEN the response is ready, the callback function would receive the response as its argument.
Primary key vs Unique key:
- A primary key is a column of table which uniquely identifies each tuple (row) in that table.
- Primary key will not accept NULL values whereas Unique key can accept one NULL value. (a unique column might have rows with NULL values)
- A table can have only primary key (column), and multiple unique keys (columns).