Building Data-Driven Web Apps with Flask and SQLAlchemy Transcripts
Chapter: Database migrations with Alembic
Lecture: Getting started with Alembic
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Now as we get started in our Alembic chapter
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we've moved to another section of our source control.
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So, let's just talk about that real quick and sync up.
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So now we're over in Chapter 11, migrations
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and we're going to be working on final
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and we're leaving you this copy of starter.
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Right now they're the same as always
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but in the end they're going to be different.
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And the way we got that was just taking the final code
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from the SQLAlchemy chapter.
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So, that's where we are.
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And I've already loaded this up in PyCharm.
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Here is our migrations project that we're going to work on.
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And if we run it, everything should be running just fine.
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Here you can see we have our new data driven version
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that we got from SQLAlchemy.
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Everything's working great.
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Now in order to use Alembic, we have to first install it.
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So, let's go over here and put it in
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as a development requirement.
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So, this is actually our first one that we're going to have.
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The idea is we take all the run time dependencies
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plus one more so we have Alembic.
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Here is another one so that's good.
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And then we're just going to go to our terminal
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make sure the virtual environment is active.
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And we saypip install -r requirements-dev.txt
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Uou can see we're downloading everything
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we need to run Alembic.
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Now, the next thing we need to do is we need to run
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an Alembic command to create the initial structure
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kind of a scaffolding type thing.
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So it's going to generate a configuration file
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some scripts that we can run
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some scripts that will be generated
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in particular for our application and so on.
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So, what we want to do is make sure that we're in the folder
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that contains our web app.
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So, we're basically in the top level folder
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next to this one.
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And the way we do this is we're going to run alembic
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and we're going to tell it to initialize the project.
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We do this once and only once
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then we store what is generated into source control.
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And we're going to set a folder here
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and the convention is, this is also alembic.
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So we say alembic init alembic.
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We run that, a bunch of stuff happens.
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It says, hey, before you can do anything
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you're going to need to edit this ini file.
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We will do that in a moment.
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Let's just look at what happened over here in the left.
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So now we got an alembic folder
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and we got an alembic.ini.
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And within the alembic folder, we've got a script
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some other details and these versions.
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As we make revisions to our database
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they're going to be stored as scripts
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as Python files in there.
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So, that's how it's going to work.
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We're going to edit this thing to get started
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and then also we actually need to work with this
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if we want to take full advantage
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of what we can do with Alembic.
