Preview
Video Player
00:00
00:00
SQLAlchemy and Flask
12:47Connect your Flask website to a database using SQLAlchemy.
[MUSIC]
0:00
Our website needs a database to
hold all of our pets.
0:04
We're going to use SQLAlchemy
to create our pets database.
0:08
Flask has a special SQLAlchemy
connection called Flask-SQLAlchemy.
0:12
Let's install it now,
0:19
pip install flask-SQLAlchemy.
0:23
There we go.
0:29
And then let's run pip freeze
> requirements.txt.
0:30
And if I pull up our requirements file,
0:34
you can see Flask-SQLAlchemy and
SQLAlchemy have been installed.
0:38
Perfect.
0:45
I'm also gonna run clear just
to clear up the console.
0:47
If you need a refresher,
0:51
I put a link in the teacher's notes to
our SQLAlchemy content, just in case.
0:52
Let's get started by looking at
the documentation for Flask-SQLAlchemy.
0:58
I did a quick Google of
Flask-SQLAlchemy and
1:03
pulled up their documentation and
clicked on Quickstart.
1:06
If I scroll down a bit,
1:12
it shows you exactly how we're
going to create our model.
1:14
At the top here, it's showing
us we are going to need Flask.
1:18
And we're gonna be creating our Flask
app inside of the models file instead
1:23
of our app file.
1:28
So we'll need to move it.
1:29
We'll also be importing SQLAlchemy,
then we'll be creating our database name.
1:31
So you can see here,
they called theirs test.db.
1:37
And then creating a db
variable using SQLAlchemy.
1:41
Our user model will take db.Model,
our columns will
1:47
be db.Column,
the data types will be db.Integer or
1:52
string, or whichever data type you need.
1:57
You're probably wondering,
where is session and
2:02
what happened to declarative base?
2:05
This line right here is
taking care of all of that.
2:07
Pretty cool, right?
2:12
So there's a few changes we're going
to have to make to our models.py file.
2:14
If it helps, keep this
documentation open for reference.
2:19
I would also bookmark it for future use.
2:23
Let's create a new file called models.py.
2:26
At the top,
we need to do our from flask import Flask,
2:36
and then from flask-sqlalchemy import
2:43
SQLAlchemy, with a capital SQL and A.
2:49
And we're also going to need datetime.
2:54
So I'm gonna go ahead and
import that at the top too,
2:59
just since we're up here already.
3:02
Now, if you remember our documentation,
3:04
we need to move our app
variable over to this file.
3:07
So we're gonna need a couple of spaces,
and then we're gonna need to take this.
3:10
And I'm gonna cut it, Make sure I save
that file and paste it over here.
3:15
Awesome.
3:23
Next, we're going to need to set up
the database file name and location.
3:26
This will be app.config.
3:29
And this is going to be,
I'm gonna check the documentation and
3:33
I'll do this so we can see compared
to what our current code is.
3:38
So it's going to need brackets and
3:43
SQLALCHEMY_DATABASE_URI and
then our location.
3:45
So actually, I'm just gonna copy this,
Ctrl+C, Ctrl+V.
3:50
There we go.
3:54
And then we'll need a string,
and this will be sqlite, colon,
3:56
three forward slashes, and
then let's call it pets.db.
4:02
And finally, the last thing we need
to add is our DB variable equals,
4:07
and this will be SQLAlchemy,
and we're gonna pass in app.
4:12
Now we can create our model for
the database.
4:17
Remember, the model creates the layout for
the table by stating what the column names
4:20
are and
the type of content inside each column.
4:24
Do a couple spaces, and
this will be class pet, and
4:30
we're gonna pass in db.Model instead
of base, colon, and let's get inside.
4:35
Now, we'll need to list out our columns,
4:44
which will be the different
inputs in our form.
4:46
First, let's create our primary key field.
4:49
This will be id = db.Column,
4:52
And it's going to be a db.Integer, and
5:01
it's going to be primary_key=True.
5:06
Awesome.
5:15
Scroll a bit.
5:18
Second, let's also create a field to hold
5:18
a timestamp when this pet
was added to our database.
5:21
We can call it created,
set it equal to db.Column.
5:26
And I'm gonna name this one Created,
5:33
that'll be the name of this column
instead of lowercase created.
5:36
It's going to be db.DateTime,
5:41
because it's going to
be a date-time object.
5:45
And we're gonna give it a default,
which is going
5:50
to be datetime.datetime.now.
5:55
And now,
6:01
typically you see datetime.datetime.now
with the parentheses at the end.
6:02
But you wanna make sure you don't include
those parentheses, you just want .now.
6:06
If you did have the parentheses,
6:12
it would call the function right
away when the models.py file is run.
6:15
And then it would never call it again,
which is not what we want.
6:19
We want the date to work every
single time we create a new entry.
6:25
This is a very common error
developers of all levels make.
6:31
So if you're taking notes,
highlight, star, or bold that.
6:35
I'm gonna save, come down to a new line.
6:40
Okay, now we'll need to create a field for
each item in our pet form.
6:44
This is gonna be a little bit of
typing now, so let's get to it.
6:48
And they're also all going
to be string columns,
6:52
since they all have short messages.
6:56
Except for the description,
which will be text, so
6:58
the user can put in a nice
long description for the pet.
7:02
So we have name = db.Column, there we go.
7:06
And that's gonna be db.String.
7:11
And string has a parenthesis so
that you can pass in, like, say,
7:13
50, if you only want a name to be
allowed to have 50 characters.
7:19
I'm not gonna set a limit,
I'm just gonna leave it as blank.
7:25
And at the beginning here,
7:29
let's also give it a string with
Name as the name of the column.
7:32
Okay, I'm gonna copy this line because,
7:37
like I said before,
these are all gonna be extremely similar.
7:40
And this will just help
us speed up a little bit.
7:44
So after name is age,
7:46
let me change this to age.
7:48
And then the next one,
7:52
breed, Breed, and
7:56
then color and Color, and
8:02
then size and Size, and
8:10
then weight, Weight.
8:17
And then after weight is the url,
8:26
URL, and then it's the url alt tag.
8:33
I'm just gonna call url_tag.
8:38
Then after that, we have the pet type.
8:45
Then after pet type, we have the gender.
8:57
Then we have whether or
not it's been spayed.
9:07
And then we have house trained.
9:15
And then finally is our description.
9:24
And then remember, this one is going
to be a text instead of a string.
9:27
So we'll need to change this to db.Text.
9:34
Whew, that was a lot of typing, but
all of our fields have been defined.
9:41
Now we've got our model all set up.
9:44
Let's also add a dunder-repr so
9:47
our pets are nicely organized when
they're printed to the console.
9:49
I'm gonna add a space here,
and then def, dunder,
9:54
repr, it will take self,
because it is a class.
9:58
And then inside,
we're going to return and f, and
10:04
I'm gonna do triple string,
we're gonna have Pet.
10:09
Then we're gonna have the Name
is equal to self.name.
10:14
And I'm gonna close out my triple string,
enter this onto the next line here.
10:20
There we go.
10:27
Then let's do Age is equal to self.age.
10:28
And then we have Breed, self.breed.
10:34
And you can see,
I'm gonna do this for all of them.
10:37
And lastly,
10:53
Description,
10:58
self.description.
11:04
Awesome.
11:13
Make sure to save your file.
11:15
And then over in app.py, we'll need
to change out our imports a bit.
11:16
We no longer need to import capital Flask
because we're importing it over here.
11:21
And we also need to bring over our app.
11:27
So let's remove, Flask from there.
11:33
And then below,
we'll need from models import,
11:38
and we'll need access to the db variable.
11:43
We'll talk about that more soon.
11:48
Need access to our Pet model and
to the app variable.
11:50
Make sure and save, and
then let's scroll down here.
11:56
And inside our dunder main,
12:01
we're going to call db.create_all.
12:05
This replaces the base.metadata.create_all
call that you've
12:10
seen in the SQLAlchemy course.
12:15
Let's save and let's go ahead and
run the file to test it all out.
12:17
Python app.py, and,
It's saying I can't import pet.
12:21
It's probably because
I gave it a lowercase.
12:24
Let's fix that, save.
12:33
Our classes should always start with
an uppercase, and let's run again.
12:36
There we go, now it's working.
12:39
And you can see,
our pets database was created.
12:41
Nice job, Pythonistas!
12:44