Now let's collect all the knowledge we have gained in one chapter.

# Models

A **Model** is a class that represents a table from the database.

### Model class structure
Model class should be inherited from the `Model` class.
```python
class NewModel(models.Model):
```




The structure of the Model class should be filled in by <a href='https://docs.djangoproject.com/en/4.2/ref/models/fields/#field-types' target='_blank'>Field</a> objects.

```python
# Example
attribute = models.IntegerField()
```

> Note
>
> Some fields have non-optional parameters (arguments).


### Manager

<a href='https://docs.djangoproject.com/en/4.2/topics/db/managers/'
target='_blank' >Manager</a> allows tools to manipulate the data.

```python
objects = models.Manager()
```

### Command for Migrations
```
python manage.py makemigrations
python manage.py migrate
```
> Note
>
> Try the `python3` if the `python` doesn't work.

# Instances

To work with instances, you need to use different methods.

### Create
1. Create a new Model class instance.
2. Fill in all necessary attributes.
3. Submit changes using the `save()` method that send a query to the database.

```python
post = Post()

post.title = "Title"
post.text = "Text"

post.save()
```

### Retrieve all
Return the iterable <a href='https://docs.djangoproject.com/en/4.2/ref/models/querysets/' target='_blank'>QuerySet</a> containing database records.

```python
posts = Post.objects.all()
```




### Retrieve one
Return the one database record as the Model class instance.

```python
post = Post.objects.get(pk=pk)
```


### Update
1. Retrieve data.
2. Reassign attributes of the Model class instance(s).
3. Submit changes using the `save()` method that send a query to the database.

```python
post = Post.objects.get(pk=pk)

post.title = "New Title"
post.text = "New text"

post.save()
```


```python
posts = Post.objects.all()

for post in posts:
    post.title = "New Title"
    post.text = "New text"

    post.save()
```


# URL patterns

To receive the `pk` from the URL address, we need to use the specific syntax: `<int:pk>`, where:
- `int` is a type of value;
- `pk` is the name of the argument in the view function.

The Django Framework is the best choice to start learning Backend Development using Python! Here you will dive into the Backend, learn how to handle HTTP requests, pass and extract data, and create HTML pages using Templates. In particular, you will learn how to use Python to interact with a database in a very convenient way without using SQL.

This section provides an introduction to Django and its key concepts. It covers the explanation of Django as a web framework, the MVT architectural pattern it follows, and the steps to initialize a new project using Django. The section also includes instructions on running the server.

If you are ready to write your first HTML page on Django - now is the time. Here you can learn how to respond to web requests using the Python programming language.

Do you think that building a database using Python is not possible? It's not true! Let's start to do it with Django!

If you already know how to build a database, then it's time to manipulate data from it. Django ORM is a tool that allows you to work with data from a database. Let's take a look at it, shall we?

The HTTP response as a string doesn't look good. It is worth correcting this by using DTL technology, which allows you to dynamically generate beautiful HTML pages and return them to the user.

You can learn how to answer requests in the previous sections but how to transfer information and process it? Passing data via HTTP request and retrieving is easy. You just have to figure it out, you can find help here.

Django: First Dive

Summary

Models

Model class structure

Manager

Command for Migrations

Instances

Create

Retrieve all

Retrieve one

Update

URL patterns