Building data-driven web apps with Flask and SQLAlchemy Transcripts
Chapter: Welcome to the course
Lecture: Course topics
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0:00
Let's quickly lay out the topics
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that we're going to cover and add
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just a little bit of background to each one of them.
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So after this chapter, we're going to quickly talk
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about how to set up your machine,
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make sure you have the right version of Python,
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the right editor and also all the starter source code
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or data that you might need to get going.
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Then we're going to talk about the Flask web framework itself
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compared to some of the other frameworks
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like Django, Pyramid, Bottle and so on,
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where does it fit in that world
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and what are some of the core elements
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or building blocks of it.
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We're going to go and create our first Flask site.
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Now, we're going to build a pretty involved
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and very cool app as we get through this course.
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But let's not start there, let's just create
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the hello world equivalent of a Flask site
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and see what all the moving parts are,
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and then build out something more interesting.
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We're going to focus on some of the techniques
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and language features of Jinja templates.
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The idea with Flask is we're going to code
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maybe to a database or a service or something like that,
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pull back some data and we want to render that to HTML.
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But you don't do that all on Python.
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Most of the HTML is fixed.
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You maybe just want to take a list
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and repeat little elements of it as HTML fragments
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or conditionally show or hide things
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like if you're logged in or not logged in.
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So we're going to talk about the Jinja template language
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and how that fits in the Flask.
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One of the first things that happen
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in these MVC, Model-View-Controller frameworks like Flask
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is that a URL request will come in
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both the verb and the URL is going to come in
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and it's up to this thing called routing
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to figure out what function is going to handle that request,
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what Python function.
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So we're going to figure out how to use routing
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to map URLs to our view methods.
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Flask doesn't do anything for making our site look good,
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it just delivers whatever HTML we write.
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So we don't want to have to write all of it.
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We're going to talk about some of the cool
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frontend frameworks,
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Bootstrap as well as a couple of others
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that we could use to make our site look better.
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And we will use some Bootstrap to make out site look good.
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Almost all the interesting web applications
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talk to some kind of data backend,
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and we're going to talk to our relational database.
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So we're going to focus on using SQLAlchemy
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and its ORM to map Python classes to the database.
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So we're going to see how to define those classes,
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how to set up the connections,
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and really do all the queries and inserts and updates,
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everything you need to do to work with SQLAlchemy.
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SQLAlchemy is great for creating
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the initial database structure.
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I have a packages and class, and I talk to SQLAlchemy
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and then create packages table in database.
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But it will not migrate it, it will not change it over time,
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and if those things become out of sync,
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your database class and your database schema,
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and the app will crash and freak out
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and say whoa, whoa, I can't work with this,
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this database is incompatible with my understanding
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of what it should be.
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So in order to evolve our database,
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our database schema,
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as things grow and change in our application,
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we need to use something called migrations.
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So we're going to use something called Alembic,
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which is paired with SQLAlchemy
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to very nicely and in many ways automatically
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evolve our database schema to stay in line
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with our application code.
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Web apps that show data, well they're fun,
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but it's way better if you can accept user input,
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let people search, let them interact with things
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and so on, create accounts, register, what not.
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So we're going to talk about HTML forms
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and how we let users submit data back
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to our Flask application.
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We're also going to see that the internet
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is a dangerous place.
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People will send us invalid data,
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either by mistake or maliciously.
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So we're going to look at a design pattern
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called view models that abstract the way
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or isolate a way the validation for all data
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coming into the server, as well as the data exchange
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with the template.
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It's going to be really, really nice.
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And on the client side, we're going to look
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at some HTML file features that will, with almost no effort,
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provide really great validation
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for at least the browsers.
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We want to make sure that our web app is working
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and stays working.
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So we're going to write some unit tests,
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we're going to use PyTest and some special infrastructure
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that is baked right into Flask
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to help us write testable code.
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You'll see that testing web applications can be tricky.
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We already talked about it, interacting with the database.
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But it also does things like interact
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with the Flask web framework itself.
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It expects a request to come in properly structured
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and so on. So we're going to talk about how we can
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either fake out some of those things
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or use a special testing infrastructure from Flask
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to make sure that we can write our tests in isolation
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the way they're meant to work.
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Once we get out app all working and we want to put it online,
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so we're going to deploy this
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to a Linux cloud virtual machine
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using Nginx, uWSGI and Ubuntu.
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You'll see that not whole lot to it
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and it's really platform to run our web app on.
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And finally, we're going to talk about converting
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our web app to MongoDB.
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As we talked about before, this is interesting
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because MongoDB is a great choice for database backend
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and it has some really great similarities
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to the SQLAlchemy, so it will be quite similar,
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but it also will show you the true power
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of some of our various design patterns
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that we're going to implement,
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and sometimes we're going to call services, our view models,
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and things like that. And we're going to be able to completely swap out
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the entire database style,
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not just implementation but even relational
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versus NoSQL or non-relational databases
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with just changing a couple of files.
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So it's going to be really great.
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It's going to be a great sort of way or grounded style
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and appreciate what we built.
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Also I'll show you how flexible our data access layer
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will have become by this point.
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Well, that's it. This is what we're going to cover.
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I think this is a great set of topics.
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Once you get through all of these,
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you're going to know pretty much everything
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that you need to know to write real true production
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data-driven web apps.
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It's going to be a lot of fun.
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I hope you're excited.
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I'm definitely excited to get started on this with you.
