User.objects.filter(email__endswith='gmail.com')

# models.py
class Person(models.Model):
    first_name = models.CharField('nome', max_length=100, unique=True)

# settings.py
INSTALLED_APPS = [
    ...
    'django_extensions',
    'myproject.core',
]

# settings.py
from pathlib import Path

from decouple import Csv, config
from dj_database_url import parse as dburl

# Build paths inside the project like this: BASE_DIR / 'subdir'.
BASE_DIR = Path(__file__).resolve().parent.parent


# Quick-start development settings - unsuitable for production
# See https://docs.djangoproject.com/en/3.1/howto/deployment/checklist/

# SECURITY WARNING: keep the secret key used in production secret!
SECRET_KEY = config('SECRET_KEY')

# SECURITY WARNING: don't run with debug turned on in production!
DEBUG = config('DEBUG', default=False, cast=bool)

ALLOWED_HOSTS = config('ALLOWED_HOSTS', default=[], cast=Csv())

...

# Database
# https://docs.djangoproject.com/en/3.1/ref/settings/#databases

default_dburl = 'sqlite:///' + str(BASE_DIR / 'db.sqlite3')
DATABASES = {
    'default': config('DATABASE_URL', default=default_dburl, cast=dburl),
}

...

LANGUAGE_CODE = 'pt-br'

TIME_ZONE = 'America/Sao_Paulo'

...

STATIC_ROOT = BASE_DIR.joinpath('staticfiles')

# urls.py
from django.contrib import admin
from django.http import HttpResponse
from django.urls import path


def index(request):
    return HttpResponse('<h1>Django Tutorial</h1>')


urlpatterns = [
    path('', index, name='index'),
    path('admin/', admin.site.urls),
]

# core/urls.py
from django.urls import path

from .views import index

app_name = 'core'

urlpatterns = [
    path('', index, name='index'),
]

# urls.py
from django.contrib import admin
from django.urls import include, path

urlpatterns = [
    path('', include('myproject.core.urls', namespace='core')),
    path('admin/', admin.site.urls),
]

# core/views.py
from django.http import HttpResponse


def index(request):
    return HttpResponse('<h1>Django Tutorial</h1>')

# core/views.py
from django.shortcuts import render


def index(request):
    template_name = 'index.html'
    return render(request, template_name)

# settings.py
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'NAME': config('POSTGRES_DB', 'postgres'),
        'USER': config('POSTGRES_USER', 'postgres'),
        'PASSWORD': config('POSTGRES_PASSWORD', ''),
        'HOST': config('DB_HOST', ''),
        'PORT': '5432',
    }
}

# settings.py
INSTALLED_APPS = [
    ...
    'myproject.core',
    'myproject.expense',
]

# core/models.py
from django.db import models


class TimeStampedModel(models.Model):
    created = models.DateTimeField(
        'criado em',
        auto_now_add=True,
        auto_now=False
    )
    modified = models.DateTimeField(
        'modificado em',
        auto_now_add=False,
        auto_now=True
    )

    class Meta:
        abstract = True

# expense/models.py
from django.db import models

from myproject.core.models import TimeStampedModel


class Customer(models.Model):
    first_name = models.CharField('nome', max_length=50)
    last_name = models.CharField('sobrenome', max_length=50, null=True, blank=True)  # noqa E501
    email = models.EmailField(null=True, blank=True)

    class Meta:
        ordering = ('first_name',)
        verbose_name = 'cliente'
        verbose_name_plural = 'clientes'

    @property
    def full_name(self):
        return f'{self.first_name} {self.last_name or ""}'.strip()

    def __str__(self):
        return self.full_name


class Expense(TimeStampedModel):
    description = models.CharField('descrição', max_length=100)
    payment_date = models.DateField('data de pagamento', null=True, blank=True)
    customer = models.ForeignKey(
        Customer,
        on_delete=models.SET_NULL,
        verbose_name='pago a',
        related_name='expenses',
        null=True,
        blank=True
    )
    value = models.DecimalField('valor', max_digits=7, decimal_places=2)
    paid = models.BooleanField('pago', default=False)

    class Meta:
        ordering = ('-payment_date',)
        verbose_name = 'despesa'
        verbose_name_plural = 'despesas'

    def __str__(self):
        return self.description

    # def get_absolute_url(self):
    #     return reverse_lazy('_detail', kwargs={'pk': self.pk})

# expense/admin.py
from django.contrib import admin

from .models import Customer, Expense

# admin.site.register(Customer)


@admin.register(Customer)
class CustomerAdmin(admin.ModelAdmin):
    list_display = ('__str__', 'email')
    search_fields = ('first_name', 'last_name', 'email')


@admin.register(Expense)
class ExpenseAdmin(admin.ModelAdmin):
    list_display = ('__str__', 'customer', 'value', 'payment_date', 'paid')
    search_fields = ('description', 'customer__first_name', 'customer__last_name')  # noqa E501
    list_filter = ('paid',)
    date_hierarchy = 'payment_date'

# expense/views.py
from django.shortcuts import render


def expense_list(request):
    template_name = 'expense/expense_list.html'
    return render(request, template_name)


def expense_detail(request, pk):
    template_name = 'expense/expense_detail.html'
    return render(request, template_name)


def expense_create(request):
    template_name = 'expense/expense_form.html'
    return render(request, template_name)

# expense/urls.py
from django.urls import path

from myproject.expense import views as v

app_name = 'expense'

urlpatterns = [
    path('', v.expense_list, name='expense_list'),
    path('<int:pk>/', v.expense_detail, name='expense_detail'),
    path('create/', v.expense_create, name='expense_create'),
]

# urls.py
...
path('expense/', include('myproject.expense.urls', namespace='expense')),
...

# expense/views.py
from .models import Expense


def expense_list(request):
    template_name = 'expense/expense_list.html'
    object_list = Expense.objects.all()
    context = {'object_list': object_list}
    return render(request, template_name, context)

# expense/models.py
from django.urls import reverse_lazy

    ...
    def get_absolute_url(self):
        return reverse_lazy('expense:expense_detail', kwargs={'pk': self.pk})

# expense/views.py
def expense_detail(request, pk):
    template_name = 'expense/expense_detail.html'
    _object = Expense.objects.get(pk=pk)
    context = {'object': _object}
    return render(request, template_name, context)

# expense/forms.py
from django import forms

from .models import Expense


class ExpenseForm(forms.ModelForm):
    required_css_class = 'required'

    payment_date = forms.DateField(
        label='Data de pagamento',
        widget=forms.DateInput(
            format='%Y-%m-%d',
            attrs={
                'type': 'date',
            }),
        input_formats=('%Y-%m-%d',),
        required=False,
    )

    class Meta:
        model = Expense
        # fields = '__all__'
        fields = ('description', 'payment_date', 'customer', 'value')
        # exclude = ('paid',)

    def __init__(self, *args, **kwargs):
        super(ExpenseForm, self).__init__(*args, **kwargs)
        for field_name, field in self.fields.items():
            field.widget.attrs['class'] = 'form-control'

# expense/views.py
from django.shortcuts import redirect, render

from .forms import ExpenseForm
from .models import Expense


def expense_create(request):
    template_name = 'expense/expense_form.html'
    form = ExpenseForm(request.POST or None)

    if request.method == 'POST':
        if form.is_valid():
            form.save()
            return redirect('expense:expense_list')

    context = {'form': form}
    return render(request, template_name, context)

# expense/urls.py
...
path('<int:pk>/update/', v.expense_update, name='expense_update'),

# expense/views.py
def expense_update(request, pk):
    template_name = 'expense/expense_form.html'
    instance = Expense.objects.get(pk=pk)
    form = ExpenseForm(request.POST or None, instance=instance)

    if request.method == 'POST':
        if form.is_valid():
            form.save()
            return redirect('expense:expense_list')

    context = {'form': form}
    return render(request, template_name, context)

# expense/urls.py
...
path('<int:pk>/delete/', v.expense_delete, name='expense_delete'),

# expense/views.py
def expense_delete(request, pk):
    template_name = 'expense/expense_confirm_delete.html'
    obj = Expense.objects.get(pk=pk)

    if request.method == 'POST':
        obj.delete()
        return redirect('expense:expense_list')

    context = {'object': obj}
    return render(request, template_name, context)

# expense/urls.py
from django.urls import path

from myproject.expense import views as v

app_name = 'expense'

urlpatterns = [
    # path('', v.expense_list, name='expense_list'),
    # path('<int:pk>/', v.expense_detail, name='expense_detail'),
    # path('create/', v.expense_create, name='expense_create'),
    # path('<int:pk>/update/', v.expense_update, name='expense_update'),
    # path('<int:pk>/delete/', v.expense_delete, name='expense_delete'),
    path('', v.ExpenseListView.as_view(), name='expense_list'),
    path('<int:pk>/', v.ExpenseDetailView.as_view(), name='expense_detail'),
    path('create/', v.ExpenseCreateView.as_view(), name='expense_create'),
    path('<int:pk>/update/', v.ExpenseUpdateView.as_view(), name='expense_update'),
    path('<int:pk>/delete/', v.ExpenseDeleteView.as_view(), name='expense_delete'),
]

# expense/views.py
from django.shortcuts import redirect, render
from django.urls import reverse_lazy
from django.views.generic import (
    CreateView,
    DeleteView,
    DetailView,
    ListView,
    UpdateView
)

...

class ExpenseListView(ListView):
    model = Expense


class ExpenseDetailView(DetailView):
    model = Expense


class ExpenseCreateView(CreateView):
    model = Expense
    form_class = ExpenseForm


class ExpenseUpdateView(UpdateView):
    model = Expense
    form_class = ExpenseForm


class ExpenseDeleteView(DeleteView):
    model = Expense
    success_url = reverse_lazy('expense:expense_list')