Detailed explanation of Model in Django framework

Django is an open source Python web framework. It adopts the MVT (Model-View-Template) architectural pattern and divides the application into three parts: Model, View and Template. Among them, Model is a basic component in the Django framework, used to define and manage data. This article will provide a detailed explanation of Model in the Django framework.

1. What is Model

In the Django framework, Model is the component responsible for defining, encapsulating, saving and managing data. Models are mainly defined in the form of Python classes, and each Model represents a database table. For example, if we want to create a user management application, we can create a Model named User, and its corresponding database table is the table named user.

In the Model, we can define the fields of the table. These fields can be integers, strings, dates, etc. Each field corresponds to a column in the table. In addition, we can also define some methods and properties for operating and managing data.

2. Model naming rules

The Model naming rules in Django are relatively simple, and they follow the naming rules of Python. The class name of the Model should start with a capital letter and be named in camel case, for example:

class MyModel(models.Model):
    name = models.CharField(max_length=50)
    age = models.IntegerField()

3. Model’s field type

In the Django framework, Model defines a series of The field type used to represent the columns in the table. Field types in Django include the following:

• CharField: string type;
• IntegerField: integer type;
• BooleanField: Boolean type;
• DecimalField: decimal floating point number type;
• DateField: date type;
• DateTimeField: date time type;
• TextField: long text type.

In addition to the above basic types, Django also supports many other types, including ArrayField, ForeignKey, OneToOneField, etc., which can describe the columns in the table in a more granular manner.

4. Field options for Model

In Django, each field type has some options that further describe the characteristics of each field. For example, the CharField type has options for specifying maximum length, nullability, default values, etc. These options can be assigned values ​​when the field is defined, for example:

class MyModel(models.Model):
    name = models.CharField(max_length=50)
    age = models.IntegerField(default=0)

In this example, the name field type is CharField, the maximum length is 50; the age field type is IntegerField, the default value is 0.

5. Model’s Meta class

Each Model class can define a Meta class for further configuration of the model. For example, you can specify the sorting method of the model, the name of the data table used, the relationship with other models, etc. A common usage is to specify the data table name and the verbose name of the model, which are used in the management background.

class MyModel(models.Model):
    name = models.CharField(max_length=50)
    age = models.IntegerField()

    class Meta:
        db_table = 'my_model'
        verbose_name = "我的模型"
        verbose_name_plural = "我的模型集合"

In this example, we use the db_table option to specify the name of the data table as my_model, use the verbose_name option to specify the Chinese name of the model as "my model", and use the verbose_name_plural option to specify the corresponding plural Chinese name. The name is "My Model Collection".

6. Methods and properties of Model

In Model, in addition to defining fields, we can also define some methods and properties for operating and managing data. For example, we can define a method to obtain the user's age group:

class User(models.Model):
    name = models.CharField(max_length=50)
    age = models.IntegerField()

    def get_age_range(self):
        if 0 <= self.age < 18:
            return "未成年"
        elif 18 <= self.age < 30:
            return "青年"
        elif 30 <= self.age < 50:
            return "中年"
        else:
            return "老年"

This method can return a string based on the user's age, indicating the user's age group, which is convenient for us to use in business logic. In addition, we can also define some attributes to quickly obtain some information about a Model. For example:

class MyModel(models.Model):
    name = models.CharField(max_length=50)
    age = models.IntegerField()

    @property
    def full_name(self):
        return "{}{}".format(self.name, self.age)

In this example, we define a full_name attribute, which returns a string composed of the name and age of the MyModel object.

7. Model's management backend

The Django framework provides an automatically generated management backend, which can be used to add, delete, modify, and check the Model. We only need to make relevant configurations in the model/admin.py file to create a management backend for each Model.

from django.contrib import admin
from .models import MyModel

admin.site.register(MyModel)

In this example, we use the admin.site.register() function to register MyModel into the management background, so that MyModel can be operated in the management background.

To sum up, the Model in the Django framework is an important component for defining and managing data. It can help us operate data conveniently and quickly build a complete application. By studying this article, we can have a deeper understanding of the various features of Model in the Django framework, helping us develop more efficiently.

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