users = User.objects.all()
print(users)

if users:
    for u in users:
         print(u)

users = User.objects.all()
print(users)
print("Cache: ", users._result_cache)

if users:
    print("Cache: ", users._result_cache)
    for u in users:
        print(u)

<QuerySet [<User: torham>]>
Cache:  None
Cache:  [<User: torham>]
torham

users = User.objects.all()
print(users)

if users:
    for u in users.values("username"):
        print(u)

>>> from django.db.models import Avg, Max, Min
>>> Book.objects.aggregate(Avg("price"), Max("price"), Min("price"))
# {'price__avg': 34.35, 'price__max': Decimal('81.20'), 'price__min': Decimal('12.99')}

SELECT AVG(Price) as price_avg FROM Books WHERE puddate='2023-01-01';

>>> from django.db.models import Avg
>>> from datetime import datetime
>>> Books.objects.filter(pubdate=datetime(2023, 1, 1)).aggregate(price_avg=Avg("price"))

If you think you're perfect already, then you never will be.

class Person(models.Model):
    first_name = models.CharField(...)
    last_name = models.CharField(...)
    birth_date = models.DateField(...)

Person.objects.raw("SELECT * FROM myapp_person")

>>> Person.objects.raw(
...     """
...     SELECT first AS first_name,
...            last AS last_name,
...            bd AS birth_date,
...            pk AS id,
...     FROM some_other_table
...     """
... )

>>> name_map = {"first": "first_name", "last": "last_name", "bd": "birth_date", "pk": "id"}
>>> Person.objects.raw("SELECT * FROM some_other_table", translations=name_map)

>>> for p in Person.objects.raw("SELECT id, first_name FROM myapp_person"):
...     print(
...         p.first_name,  # This will be retrieved by the original query
...         p.last_name,  # This will be retrieved on demand
...     )
...

from django.db import connection


def my_custom_sql(self):
    with connection.cursor() as cursor:
        cursor.execute("UPDATE bar SET foo = 1 WHERE baz = %s", [self.baz])
        cursor.execute("SELECT foo FROM bar WHERE baz = %s", [self.baz])
        row = cursor.fetchone()

    return row

def dictfetchall(cursor):
    """
    Return all rows from a cursor as a dict.
    Assume the column names are unique.
    """
    columns = [col[0] for col in cursor.denoscription]
    return [dict(zip(columns, row)) for row in cursor.fetchall()]

@transaction.atomic()
def something():
     do_database_update()
     do_database_delete()

def something():
     with transaction.atomic():
            do_database_update()
            do_database_delete()

with transaction.atomic():
       do_update():
       with transaction.atomic():
               do_delete()

def something():

     with transaction.atomic():
            transaction.on_commit(send_mail)

from rest_framework import serializers

class DepositSerializer(serializers.Serializer):
    amount = serializers.IntegerField()

    def validate_amount(self, value):
        
        if value <= 0:
            raise serializers.ValidationError("pls enter a number bigger than zero.")
        return value