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How do I create a ListField in Django (Python) like the ListProperty property in Google App Engine (Python)? My data is a list like this : 3,4,5,6,7,8.
What property do I have to define and how would I fetch values from it?
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Fields in Django are the data types to store a particular type of data. For example, to store an integer, IntegerField would be used. These fields have in-built validation for a particular data type, that is you can not store “abc” in an IntegerField. Similarly, for other fields.
If you are using Google App Engine or MongoDB as your backend, and you are using the djangoappengine library, there is a built in ListField that does exactly what you want. Further, it's easy to query the Listfield to find all objects that contain an element in the list.
Django Model Fields Django version 2.2 offers 26 different field types to capture different data formats.
Django model data types and fields list. The most important part of a model and the only required part of a model is the list of database fields it defines. Fields are specified by class attributes. Be careful not to choose field names that conflict with the models API like clean, save, or delete.
ListField in serializers - Django REST Framework - GeeksforGeeks. ListField. ListField is basically a list field that validates the input against a list of objects. How to use ListField in Serializers ? Validation on ListField. Advanced concepts.
Each field in the model should be an instance of the appropriate Field class. Django uses field class types to determine a few things: The column type, which tells the database what kind of data to store (e.g. INTEGER, VARCHAR, TEXT).
Adding search_fields to Django Admin 4. Conclusion First, let's create a model that we'll work with it. Let's now register our model in admin.py. As you can see, our model has been registered, now let's add some products to our model. in this image, Django displayed just the field name that we have returned in the __str__ method.
Revisiting this with a ListField type you can use. But it makes a few of assumptions, such as the fact that you're not storing complex types in your list. For this reason I used ast.literal_eval() to enforce that only simple, built-in types can be stored as members in a ListField:
from django.db import models import ast class ListField(models.TextField): __metaclass__ = models.SubfieldBase description = "Stores a python list" def __init__(self, *args, **kwargs): super(ListField, self).__init__(*args, **kwargs) def to_python(self, value): if not value: value = [] if isinstance(value, list): return value return ast.literal_eval(value) def get_prep_value(self, value): if value is None: return value return unicode(value) def value_to_string(self, obj): value = self._get_val_from_obj(obj) return self.get_db_prep_value(value) class Dummy(models.Model): mylist = ListField() Taking it for a spin:
>>> from foo.models import Dummy, ListField >>> d = Dummy() >>> d.mylist [] >>> d.mylist = [3,4,5,6,7,8] >>> d.mylist [3, 4, 5, 6, 7, 8] >>> f = ListField() >>> f.get_prep_value(d.numbers) u'[3, 4, 5, 6, 7, 8]' There you have it that a list is stored in the database as a unicode string, and when pulled back out it is run through ast.literal_eval().
Previously I suggested this solution from this blog post about Custom Fields in Django:
An alternative to the CommaSeparatedIntegerField, it allows you to store any separated values. You can also optionally specify a token parameter.
from django.db import models class SeparatedValuesField(models.TextField): __metaclass__ = models.SubfieldBase def __init__(self, *args, **kwargs): self.token = kwargs.pop('token', ',') super(SeparatedValuesField, self).__init__(*args, **kwargs) def to_python(self, value): if not value: return if isinstance(value, list): return value return value.split(self.token) def get_db_prep_value(self, value): if not value: return assert(isinstance(value, list) or isinstance(value, tuple)) return self.token.join([unicode(s) for s in value]) def value_to_string(self, obj): value = self._get_val_from_obj(obj) return self.get_db_prep_value(value) Try using a CommaSeparatedIntegerField which is documented here: http://docs.djangoproject.com/en/1.2/ref/models/fields/#commaseparatedintegerfield
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