CharField is a string field, for small- to large-sized strings. It is like a string field in C/C++. CharField is generally used for storing small strings like first name, last name, etc. To store larger text TextField is used. The default form widget for this field is TextInput.
CharField has one extra required argument:
CharField.max_length
The maximum length (in characters) of the field. The max_length is enforced at the database level and in Django’s validation using MaxLengthValidator.
Syntax:
field_name = models.CharField(max_length=200, **options)
Django Model CharField Explanation
Illustration of CharField using an Example. Consider a project named neveropen having an app named Lazyroar.
Refer to the following articles to check how to create a project and an app in Django.
Enter the following code into models.py file of Lazyroar app.
Python3
from django.db import modelsfrom django.db.models import Model# Create your models here.class GeeksModel(Model): Lazyroar_field = models.CharField(max_length = 200) |
Add the Lazyroar app to INSTALLED_APPS
Python3
# Application definitionINSTALLED_APPS = [ 'django.contrib.admin', 'django.contrib.auth', 'django.contrib.contenttypes', 'django.contrib.sessions', 'django.contrib.messages', 'django.contrib.staticfiles', 'Lazyroar',] |
Now when we run makemigrations command from the terminal,
Python manage.py makemigrations
A new folder named migrations would be created in Lazyroar directory with a file named 0001_initial.py
Python3
# Generated by Django 2.2.5 on 2019-09-25 06:00from django.db import migrations, modelsclass Migration(migrations.Migration): initial = True dependencies = [ ] operations = [ migrations.CreateModel( name ='GeeksModel', fields =[ ('id', models.AutoField( auto_created = True, primary_key = True, serialize = False, verbose_name ='ID' )), ('Lazyroar_field', models.CharField( max_length = 200, )), ], ), ] |
Now run,
Python manage.py migrate
Thus, an Lazyroar_field CharField is created when you run migrations on the project. It is a field to store small- to large-sized strings.
How to use CharField ?
CharField is used for storing small sized strings in the database. One can store First Name, Last Name, Address Details, etc. CharField should be given an argument max_length for specifying the maximum length of string it is required to store. In production server, after the Django application is deployed, space is very limited. So it is always optimal to use max_length according to the requirement of the field. Let us create an instance of the CharField we created and check if it is working.
Python3
# importing the model# from Lazyroar appfrom Lazyroar.models import GeeksModel# creating a instance of# GeeksModelgeek_object = GeeksModel.objects.create(Lazyroar_field ="GFG is Best")geek_object.save() |
Now let’s check it in admin server. We have created an instance of GeeksModel.
Field Options
Field Options are the arguments given to each field for applying some constraint or imparting a particular characteristic to a particular Field. For example, adding an argument null = True to CharField will enable it to store empty values for that table in a relational database.
Here are the field options and attributes that an CharField can use.
| Field Options | Description |
|---|---|
| Null | If True, Django will store empty values as NULL in the database. Default is False. |
| Blank | If True, the field is allowed to be blank. Default is False. |
| db_column | The name of the database column to use for this field. If this isn’t given, Django will use the field’s name. |
| db_index | If True, a database index will be created for this field |
| db_tablespace | The name of the database tablespace to use for this field’s index, if this field is indexed. The default is the project’s DEFAULT_INDEX_TABLESPACE setting, if set, or the db_tablespace of the model, if any. If the backend doesn’t support tablespaces for indexes, this option is ignored. |
| Default | The default value for the field. This can be a value or a callable object. If callable it will be called every time a new object is created. |
| help_text | Extra “help” text to be displayed with the form widget. It’s useful for documentation even if your field isn’t used on a form. |
| primary_key | If True, this field is the primary key for the model. |
| editable | If False, the field will not be displayed in the admin or any other ModelForm. They are also skipped during model validation. Default is True. |
| error_messages | The error_messages argument lets you override the default messages that the field will raise. Pass in a dictionary with keys matching the error messages you want to override. |
| help_text | Extra “help” text to be displayed with the form widget. It’s useful for documentation even if your field isn’t used on a form. |
| verbose_name | A human-readable name for the field. If the verbose name isn’t given, Django will automatically create it using the field’s attribute name, converting underscores to spaces. |
| validators | A list of validators to run for this field. See the validators documentation for more information. |
| Unique | If True, this field must be unique throughout the table. |
