Django Cheatsheet by Sai Krishna

Basic Settings
Basic Login System
CustomUser Model
Actions in Admin for models
Choices type in Models
Messages in Django Templates
Transaction Atomic
Time in IST
Humanize Date and Time

Basic Settings

settings.py in Main App Folder

# At the start
import os
from django.contrib.messages import constants as message_constants

# Replace Original
TIME_ZONE = 'Asia/Kolkata'

# Under the Static declaration 
STATICFILES_DIRS = [
    os.path.join(BASE_DIR, "static")
]

# At the end
MESSAGE_TAGS = {
    message_constants.ERROR: 'danger',
}

Add in Template DIRS settings.py in Main App Folder
```
os.path.join(BASE_DIR, "templates")
```
Add in Installed Apps settings.py in Main App Folder
```
'home.apps.HomeConfig'
```

import these in views.py file in Home App

from django.shortcuts import redirect, render, HttpResponse
from django.contrib.auth import authenticate, login, logout
from django.contrib import messages

views.py file in Home App

# Index Handler
def index(request):
    if request.user.is_anonymous:
        return redirect("/login")
    return render(request, "index.html", {"active": "home"})
                
# Login Handler
def loginUser(request):
    if request.method != "POST":
        return HttpResponse("Invalid Method")
    username = request.POST.get("username")
    password = request.POST.get("password")
    rememberme = request.POST.get("rememberme")
    if not rememberme:
        request.session.set_expiry(0)
    else:
        request.session.set_expiry(86400)
    user = authenticate(username=username, password=password)
    if user is not None:
        login(request, user)
        messages.add_message(request, messages.SUCCESS, 'Login Successfull')
        return redirect("/")
    messages.add_message(request, messages.ERROR, 'Invalid Username or Password')
    return redirect("/login")

# Login View
def loginView(request):
    if request.user.is_authenticated:
        return redirect("/")
    return render(request, "login.html")

# Logout Handler
def logoutUser(request):
    logout(request)
    return redirect("/")

# About page, for illustrative purpose only
def about(request):
    if request.user.is_anonymous:
        return redirect("/login")
    return render(request, "about.html", {"active": "about"})

Add this on top in urls.py in Main App
```
from django.conf.urls import include
```
Add this in urlpatterns in urls.py in Main App
```
path('', include('home.urls')),
```

urls.py in Home App

from django.urls import path
from .views import index, loginUser, loginView, logoutUser, about

urlpatterns = [
    path('', index),
    path('login', loginView, name="Login View"),
    path('loginUser', loginUser, name="Login Authenticator"),
    path('logout', logoutUser, name="Logout"),
    path('about', about, name="About"),
]

<!doctype html>
<html lang="en">

<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <meta name="description" content="Login to Examsite by Sai Krishna">
    <meta name="author" content="Sai Krishna">
    <title>Login</title>
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.2.1/css/bootstrap.min.css" integrity="sha384-GJzZqFGwb1QTTN6wy59ffF1BuGJpLSa9DkKMp0DgiMDm4iYMj70gZWKYbI706tWS" crossorigin="anonymous">
    <link defer rel="stylesheet" href="/static/bootstrap-5.0.1/css/bootstrap.min.css"> 
    <!-- Theme colour -->
    <!--meta name="theme-color" content="#7952b3"-->

    <style>
    .bd-placeholder-img {
        font-size: 1.125rem;
        text-anchor: middle;
        -webkit-user-select: none;
        -moz-user-select: none;
        user-select: none;
    }

    @media (min-width: 768px) {
        .bd-placeholder-img-lg {
        font-size: 3.5rem;
        }
    }

    html, body {
        height: 100%;
    }

    body {
        display: flex;
        align-items: center;
        padding-top: 40px;
        padding-bottom: 40px;
        background-color: #f5f5f5;
    }

    .form-signin {
        width: 100%;
        max-width: 330px;
        padding: 15px;
        margin: auto;
    }

    .form-signin .checkbox {
        font-weight: 400;
    }

    .form-signin .form-floating:focus-within {
        z-index: 2;
    }

    .form-signin input[type="email"] {
        margin-bottom: -1px;
        border-bottom-right-radius: 0;
        border-bottom-left-radius: 0;
    }

    .form-signin input[type="password"] {
        margin-bottom: 10px;
        border-top-left-radius: 0;
        border-top-right-radius: 0;
    }
    </style>


</head>

<body class="text-center">

    <main class="form-signin">
    <form method="post" action="/loginUser">
        {% csrf_token %}
        <img class="mb-4" src="/static/home/logo.png" alt="Logo" width="72" height="72">
        <h1 class="h3 mb-3 fw-normal">Please sign in</h1>
        {% if messages %}
        {% for message in messages %}
        <div {% if message.tags %} class="alert alert-{{ message.tags }} alert-dismissible fade show" {% endif %}
        role="alert">
        {{ message }}
        <button type="button" class="close py-3" data-dismiss="alert" aria-label="Close">
            <span aria-hidden="true">×</span>
        </button>
        </div>
        {% endfor %}
        {% endif %}
        <div class="form-floating">
        <input type="text" name="username" class="form-control" id="username" placeholder="Username">
        <label for="floatingInput">Username</label>
        </div>
        <div class="form-floating">
        <input type="password" name="password" class="form-control" id="password" placeholder="Password">
        <label for="floatingPassword">Password</label>
        </div>

        <div class="checkbox mb-3">
        <label>
            <input type="checkbox" name="rememberme" value="True"> Remember me
        </label>
        </div>
        <button class="w-100 btn btn-lg btn-primary" type="submit">Sign in</button>
        <div class="mt-4">
        New User? <a href="/signup" style="text-decoration: none;">Register Here.</a>
        </div>
        <p class="mt-3 mb-3 text-muted">© 2020–2021</p>
    </form>
    </main>
    <!-- Optional JavaScript -->
    <!-- jQuery first, then Popper.js, then Bootstrap JS -->
    <script src="/static/jquery-3.6.0.min.js"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.6/umd/popper.min.js" integrity="sha384-wHAiFfRlMFy6i5SRaxvfOCifBUQy1xHdJ/yoi7FRNXMRBu5WHdZYu1hA6ZOblgut" crossorigin="anonymous"></script>
    <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.2.1/js/bootstrap.min.js" integrity="sha384-B0UglyR+jN6CkvvICOB2joaf5I4l3gm9GU6Hc1og6Ls7i6U/mkkaduKaBhlAXv9k" crossorigin="anonymous"></script>
    <!-- <script src="/static/bootstrap-5.0.1/js/bootstrap.min.js"></script> -->

</body>

</html>

index.html in Templates

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Title</title>
</head>
<body>
    Hello World
</body>
</html>

CustomUser Model

models.py in Home

from django.db import models
from django.contrib.auth.models import AbstractUser, User
from django.urls import reverse

# Create your models here.

# Overriding the Default Django Auth User and adding One More Field (user_type)
class CustomUser(AbstractUser):
    userid = models.IntegerField(primary_key=True, unique=True)

forms.py in Home

from django import forms
from django.contrib.auth.forms import UserCreationForm
from .models import CustomUser

class CustomUserCreationForm(UserCreationForm):
    class Meta(UserCreationForm.Meta):
        model = CustomUser
        fields = "__all__"

admin.py in Home

from django.contrib import admin
from django.contrib.auth.admin import UserAdmin
from django.db import transaction
from .models import CustomUser
from .forms import CustomUserCreationForm

# Register your models here.

class CustomUserAdmin(UserAdmin):
    model = CustomUser
    add_form = CustomUserCreationForm
    list_display = ['username', 'email', 'first_name', 'last_name', 'is_staff' #Add more]
    fieldsets = (
        *UserAdmin.fieldsets,
        (
            'User Role', {
                'fields': ('user_type', 'userid')
            }
        )
    )
    
admin.site.register(CustomUser, CustomUserAdmin)

settings.py in Main App
```
AUTH_USER_MODEL = 'home.CustomUser'
```

Import in views.py if required in Home

from django.contrib.auth.hashers import make_password
from django.db import IntegrityError

Create new user in views.py in Home

def createNewUser(request):
    if request.method!="POST":
        return HttpResponse("Invalid Method GET")
    data = json.loads(request.body.decode("utf-8"))
    first_name = data["first_name"]
    last_name = data["last_name"]
    email = data["email"]
    username = data["username"]
    password = data["password"]
    try:
        u = CustomUser()
        u.first_name=first_name
        u.last_name=last_name
        u.email=email
        u.username=username
        u.password=make_password(password)
        u.save()
        context = {"message": "User Created Successfully", "status": 200}
    except IntegrityError:
        context = {"message": "Sorry, this Username already exists", "status": 500}
    except Exception as e:
        context = {"message": str(e), "status": 500}
    return HttpResponse(json.dumps(context), content_type="application/json")

Actions in Admin for models

Add these to admin.py after imports

# Add these to admin.py after imports
@transaction.atomic
def custom_action(modeladmin, request, queryset):
    for obj in queryset:
        # Change the obj data here like obj.somefield = something and last obj.save()
custom_action.short_description = 'Cutsom Action for Models'

Add this to admin.py in the Model Admin
```
actions = [ custom_action ]
```

Choices type in Models

Add these to models.py in required Model

FIELD_CHOICES = ((1, "Choice 1"), (2, "Choice 2"), (3, "Choice 3"))
field = models.IntegerField(default=1, choices=FIELD_CHOICES)

Messages in Django Templates

Import messages in views.py where required
```
from django.contrib import messages
```

Add this in the view in which you want messages

messages.add_message(request, messages.SUCCESS, 'Your message here')

Add these where messages are to be placed in Django Templates

{% if messages %}
{% for message in messages %}
<div {% if message.tags %} class="alert alert-{{ message.tags }} alert-dismissible fade show" {% endif %}
role="alert">
{{ message }}
<button type="button" class="close py-3" data-dismiss="alert" aria-label="Close">
    <span aria-hidden="true">×</span>
</button>
</div>
{% endfor %}
{% endif %}

Transaction Atomic

Add this in views.py at top
```
from django.db import transaction
```

Use this in views.py where required

# Transaction Atomic
@transaction.atomic
def function_name(request):
    pass

Time in IST

Add this in views.py at top
```
from pytz import timezone
```

Use this where time is required in IST

datetimeobj.astimezone(timezone('Asia/Kolkata')).strftime('%b. %d, %Y, %I:%M %p')

Humanize Date and Time

Add this in Installed Apps in settings.py
```
'django.contrib.humanize'
```

Use this where humanize filter is required

{% load humanize %}
{{ datetimeobject|naturaltime }}

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