Building Data-Driven Web Apps with Pyramid and SQLAlchemy Transcripts
Chapter: Modeling data with SQLAlchemy classes
Lecture: SQLAlchemy model base class
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Now for SQLAlchemy to work right
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we need to put a base class here.
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It needs to be a special one.
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Every class that maps to the same database
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needs to use the same base class.
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You can have different ones, like if you have
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an analytics database, and you have a core data database
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those might be different classes
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but all the ones that go into one database
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they should be the same.
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Okay, so how do we do that?
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Well, we're going to define a class
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and it's really quite simple.
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You sort of create one and only one of them
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from SQLAlchemy.
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So I'm going to put that into its own separate file, now.
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I think this one totally justifies its own file.
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What I'm going to do here is pushing the limit
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of maybe this is a little too fine grained
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but there's only one and it's supposed to be shared.
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So I think what I'm going to do is, do this.
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Create a model base class and then we have to
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import SQLAlchemy.extensions.declarative
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I'll just say, shorts we don't have to say
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too much there just, as dict then I'm going to
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create a class called SQLAlchemyBase.
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This class is the class that's going to be the base class
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but instead of defining it this way
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we use a factory method out of this place here
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so we say, declarative_base like that.
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And that's it.
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This is now our base type.
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It gets created at runtime by SQLAlchemy
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and then, by virtue of deriving from it, it basically means
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we're telling SQLAlchemy, "Here's another class that you're managing."
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So for example, put that here and let PyCharm import it.
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So for the top, we have from model base, import this
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and those two lines are going to pretty much be the same
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for all of our types.
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And that's it, this class can now be loaded and saved
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from the database once we connect to it.
