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@aybruhm
Forked from jacklinke/cheatsheet.py
Created April 14, 2021 14:47
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Django models cheatsheet
import uuid
from django.db import models
# Use the import below instead, if using GeoDjango fields
# from django.contrib.gis.db import models
from django.utils.translation import ugettext_lazy as _
from django.contrib.postgres.fields import (
ArrayField,
CICharField,
CIEmailField,
CITextField,
HStoreField,
IntegerRangeField,
BigIntegerRangeField,
DecimalRangeField,
DateTimeRangeField,
DateRangeField,
)
def file_directory_path(instance, filename):
# file will be uploaded to MEDIA_ROOT/my_files/{id}/{year}/{month}/{filename}
return f"my_files/{instance.id}/{timezone.now().date().strftime('%Y/%m')}/{filename}"
def create_rand_value(app_label, model_name, prefix=None, suffix_len=10):
"""
Just an example function, used to demonstrate overriding save()
It generates an easily readable, unique string
"""
code = ""
if prefix is not None:
code = code.join(prefix).join("-")
while True:
code = code.join(random.SystemRandom().choice("23456789BCDFGHJKMNPQRSTVWXYZ") for _ in range(suffix_len))
Model = apps.get_model(app_label=app_label, model_name=model_name)
try:
present = Model.objects.first()
except Model.DoesNotExist:
present = None
if present is not None:
if not Model.objects.filter(code=code).exists():
return code
# https://docs.djangoproject.com/en/3.1/topics/db/managers/#from-queryset
class MyModelQuerySet(models.QuerySet):
"""Used when we need to return a queryset that has been filtered in some way"""
def manager_and_queryset_method(self):
return
class MyModelManager(models.Manager):
"""Used when we need a table-level method that does NOT return a queryset"""
def manager_only_method(self):
return
CombinedMyModelManager = MyModelManager.from_queryset(MyModelQuerySet)
class MyModel(models.Model):
"""Comment"""
class CompanyType(models.TextChoices):
PUBLIC_LIMITED_COMPANY = 'PLC', _('Public Limited Company')
PRIVATE_COMPANY_LIMITED = 'LTD', _('Private Company limited by shares')
LIMITED_LIABILITY_PARTNERSHIP = 'LLP', _('Limited Liability Partnership')
__empty__ = _('(Unknown)')
# https://docs.djangoproject.com/en/3.1/ref/models/fields/
boolean_field = models.BooleanField(_("Boolean"), default=False)
char_field = models.CharField(_("Character"), max_length=100, blank=True)
char_field_choice = models.CharField(_("Character Choices"), choices=CompanyType.choices, default=CompanyType.__empty__, max_length=100, blank=True)
date_field = models.DateField(_("Date"), null=True, blank=True)
datetime_field = models.DateTimeField(_("DateTime"), null=True, blank=True)
decimal_field = models.DecimalField(_("Decimal"), max_digits=5, decimal_places=2, null=True)
duration_field = models.DurationField(_("Duration"), )
email_field = models.EmailField(_("Email"), max_length=254, blank=True)
file_field = models.FileField(_("File"), upload_to=file_directory_path, max_length=100)
float_field = models.FloatField(_("Float"), null=True)
generic_ip_address_field = models.GenericIPAddressField(_("Generic IP"), protocol='both', unpack_ipv4=False, null=True) # 'both', 'IPv4' or 'IPv6'
image_field = models.ImageField(_("Image"), upload_to=file_directory_path, height_field=None, width_field=None, max_length=100)
integer_field = models.IntegerField(_("Number"), null=True)
json_field = models.JSONField(_("JSONField"), default=dict)
pos_int_field = models.PositiveIntegerField(_("Positive Integer"), )
pos_small_int_field = models.PositiveSmallIntegerField(_("Positive Small Integer"), )
slug_field = models.SlugFiels(_("Slug"), max_length=50, blank=True)
small_int_field = models.SmallIntegerField(_("Small Integer"), )
text_field = models.TextField(_("Text"), blank=True)
time_field = models.TimeField(_("Time"), null=True, blank=True)
url_field = models.URLField(_("URL"), max_length=200,)
uuid_field = models.UUIDField(_("UUID"), default=uuid.uuid4)
# Relationships
# https://docs.djangoproject.com/en/3.1/ref/models/fields/#module-django.db.models.fields.related
oto = models.OneToOneField(AA, on_delete=models.CASCADE, null=True, blank=True)
fk = models.ForeignKey(BB, on_delete=models.CASCADE, related_name="xxs", null=True, blank=True)
mtm = models.ManyToManyField(CC, blank=True)
# Auto-date fields
# https://docs.djangoproject.com/en/3.1/ref/models/fields/#datefield
created = models.DateTimeField(_("DateTime Created"), auto_now_add=True, help_text=_("When this item was created"))
modified = models.DateTimeField(_("DateTime Modified"), auto_now=True, help_text=_("When this item last updated"))
# Postgres-specific range fields
# https://docs.djangoproject.com/en/3.1/ref/contrib/postgres/fields/
integer_range_field = IntegerRangeField(_("IntegerRange"))
big_integer_range_field = BigIntegerRangeField(_("BigIntegerRange"))
decimal_range_field = DecimalRangeField(_("DecimalRange"))
date_time_range_field = DateTimeRangeField(_("DateTimeRange"))
date_range_field = DateRangeField(_("DateRange"))
# GeoDjango fields
# https://docs.djangoproject.com/en/3.1/ref/contrib/gis/model-api/
point = models.PointField(srid=4326)
multi_point = models.MultiPointField()
polygon = models.PolygonField()
multi_polygon = models.MultiPolygonField()
linestring = models.LineStringField()
multi_linestring = models.MultiLineStringField()
geometry_collection = models.GeometryCollectionField()
raster = models.RasterField()
objects = CombinedMyModelManager()
class Meta:
# https://docs.djangoproject.com/en/3.1/ref/models/options/
verbose_name = _("My Model")
verbose_name_plural = _("My Models")
# abstract = True # https://docs.djangoproject.com/en/3.1/topics/db/models/#abstract-base-classes
# proxy = True # https://docs.djangoproject.com/en/3.1/topics/db/models/#proxy-models
db_table = 'my_model'
# Specifies the default field(s) to use in your model Manager’s latest() and earliest() methods.
get_latest_by = ['-datetime_field']
# The default ordering for the object, for use when obtaining lists of objects:
ordering = ['-datetime_field']
unique_together = [
['char_field', 'slug_field']
]
index_together = [
["created", "char_field"],
]
# https://docs.djangoproject.com/en/3.1/ref/models/indexes/
indexes = [
models.Index(fields=['char_field', 'text_field']),
models.Index(fields=['url_field'], name='url_field_idx'),
]
# https://docs.djangoproject.com/en/3.1/ref/models/constraints/
constraints = [
models.CheckConstraint(check=models.Q(integer_field__gte=18), name='integer_gte_18'),
models.UniqueConstraint(fields=['created', 'slug_field'], name='unique_slug_created'),
models.UniqueConstraint(
fields=['fk'],
condition=Q(char_field_choice=CompanyType.LIMITED_LIABILITY_PARTNERSHIP),
name='unique_llc_for_fk'
),
]
def __str__(self):
# https://docs.djangoproject.com/en/3.1/ref/models/instances/#str
return f'{self.char_field} {self.char_field}'
def save(self, *args, **kwargs):
# https://docs.djangoproject.com/en/3.1/topics/db/models/#overriding-model-methods
if not self.pk: # this will ensure that the object is new
self.slug_field = create_rand_value(
app_label=self._meta.app_label,
model_name=self.__class__.__name__,
prefix="",
suffix_len=10
)
super().save(*args, **kwargs)
def get_absolute_url(self):
# https://docs.djangoproject.com/en/3.1/ref/models/instances/#get-absolute-url
from django.urls import reverse
return reverse('people.views.details', args=[str(self.id)])
@property
# https://docs.djangoproject.com/en/3.1/glossary/#term-property
def char_slug(self):
return self.char_field.lower().replace(' ','-')
def process_invoices(self):
do_something()
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