How To Implement Django Authenticate For Django Login Example

This example will show you how to add django authenticate function when you implement a django login example.

1. Install Third Party Library django-simple-captcha.

1.1 Precondition.

  1. Open terminal and run below pip command to install django-simple-captcha and Pillow.
    pip install django-simple-captcha
    pip install Pillow
  2. Add captcha in Django project file INSTALLED_APPS section.
  3. Execute below python command in terminal.
    python migrations
    python migrate
  4. Add captcha url in Django project’s file urlpatterns section like below.
    # this is the url that generate captcha code and image.
    url(r'^captcha/', include('captcha.urls'))

2. Django Login Example Source Code.


2.1 Captcha Form Source Code.

Below source code will create a django login form. The form has three form fields: username, password, and a captcha field ( captcha code input box and captcha image ).

# Import django forms module.
from django import forms

# Import CaptchaField filed type.
from captcha.fields import CaptchaField

# The custom CaptchaForm class extends forms.Form class.
class CaptchaForm(forms.Form):
    # Create form field username and password
    username = forms.CharField(max_length=100, label='username')
    password = forms.FloatField(max_value=100, label='password')

    # Create a CaptchaField object in the form to generate captcha code input box, as well as the captcha image.
    # If user input verification code is incorrect, then it will display the error message "Verification code is not correct, input again."
    captcha = CaptchaField(error_messages={"invalid": u"Verification code is not correct, input again."})

2.2 LoginView and CreateCaptchaCodeView Source Code.

LoginView will be invoked when user submit login data, CreateCaptchaCodeView will be invoked when client use ajax to request a new captcha code and image.

# The LoginView class extends django View class.
class LoginView(View):

    # Process get request, when user access the LoginView with get method, then display login.html to client.
    def get(self, request):
        # Create an instance of CapatchaForm class.
        login_form = CaptchaForm()
        # Return login.html to client.
        return render(request, "login.html", locals())

    # Process post request, when user submit username, password and captcha code to LoginView then this method will be invoked.
    def post(self, request):
        # Create a CaptchaForm object.
        login_form = CaptchaForm(request.POST)

        # Get user input captcha code.
        captcha_code = request.POST.get("code")

        # If the user input captcha equals the generated captcha code.
        if captcha_code.upper() == request.session['captcha_code'].upper():
            # Get username and password value.
            username = request.POST.get("username", "")
            password = request.POST.get("password", "")
            # Direct user to login_success.html file.
            return render(request, "login_success.html")
            # If user captcha verify failed, then redirect user to login.html file again.
            return render(request, "login.html", {'msg': "Wrong captcha code"})

# Captcha generation view, invoke this view to generate the captcha image and code.
class CreateCaptchaCodeView(View):

    # Process get request.
    def get(self, request):
        # Create the captcha code and image. You can see the create_captcha_code method source code at below.
        img_obj, code = create_captcha_code()

        # Save the created image in BytesIO stream object.
        stream = BytesIO(), 'png')
        # Save the generated captcha code in session.
        request.session['captcha_code'] = code

        # Return the captcha image.
        return HttpResponse(stream.getvalue())

2.3 The create_captcha_code() Method Source Code.

This method will create the captcha verification code and image.

# Import random class.
import random

# Import captcha used image module and class from Pillow package.
from PIL import Image, ImageDraw, ImageFont, ImageFilter

# Lowercase letters, remove the i, l, o, and z that might interfere
_letter_cases = "abcdefghjkmnpqrstuvwxy"
# Uppercase letters.
_upper_cases = _letter_cases.upper()
# Numbers.
_numbers = ''.join(map(str, range(0, 10)))

# Create captcha code used letters and numbers.
init_chars = ''.join((_letter_cases, _upper_cases, _numbers))

 @todo: The create_captcha_code method will generate the captcha code and image. 
 @param size: Captcha image size(width, height),default value is(120, 30)
 @param chars: Allowed character set.
 @param img_type: Captcha image format, default is GIF, optional for GIF, JPEG, TIFF, PNG.
 @param mode: Captcha image mode, default is RGB
 @param bg_color: The background color, white is default color.
 @param fg_color: The foreground color, the CAPTCHA character color, default is blue #0000FF
 @param font_size: Captcha code font size.
 @param font_type: Captcha font, default to AE_ALARABIYA.TTF.
 @param length: Number of Captcha characters.
 @param draw_lines: Whether to draw interference lines.
 @param n_lines: The number range of interference lines, tuple value, default is (1, 2), only valid when draw_lines is True.
 @param draw_points: Whether to draw interference points.
 @param point_chance: The probability of interference point, range is [0, 100]
 @return: [0]: PIL Image instace
 @return: [1]: CAPTCHA code in image.
def create_captcha_code(size=(120, 30),
                         bg_color=(255, 255, 255),
                         fg_color=(0, 0, 255),
                         n_line=(1, 2),

    # Get the cpatcha image width and height.
    width, height = size 

    # Create captcha image object.
    img =, size, bg_color)

    # Create the draw image object.
    draw = ImageDraw.Draw(img)

    # Generates a string of given length.
    def get_chars():
        return random.sample(chars, length)

    # Draw interference line.
    def create_lines():
        # Number of interference lines.
        line_num = random.randint(*n_line)
        for i in range(line_num):
            # Start point.
            begin = (random.randint(0, size[0]), random.randint(0, size[1]))
            # End point.
            end = (random.randint(0, size[0]), random.randint(0, size[1]))
            draw.line([begin, end], fill=(0, 0, 0))

    # Draw interference point.
    def create_points():
        # Limit size to [0, 100].
        chance = min(100, max(0, int(point_chance)))

        for w in range(width):
            for h in range(height):
                tmp = random.randint(0, 100)
                if tmp > 100 - chance:
                    draw.point((w, h), fill=(0, 0, 0))

    # Draws a CAPTCHA character.
    def create_strs():
        c_chars = get_chars()
        # Each character is separated by a space
        strs = ' %s ' % ' '.join(c_chars)

        font = ImageFont.truetype(font_type, font_size)
        font_width, font_height = font.getsize(strs)

        draw.text(((width - font_width) / 3, (height - font_height) / 3),
                    strs, font=font, fill=fg_color)

        return ''.join(c_chars)

    if draw_lines:
    if draw_points:

    strs = create_strs()

    # Figure twist parameters.
    params = [1 - float(random.randint(1, 2)) / 100,
              1 - float(random.randint(1, 10)) / 100,
              float(random.randint(1, 2)) / 500,
              float(random.randint(1, 2)) / 500

    # Create a twist image.
    img = img.transform(size, Image.PERSPECTIVE, params)

    # Filter, boundary enhancement (larger threshold).
    img = img.filter(ImageFilter.EDGE_ENHANCE_MORE)

    return img, strs

2.4 Html File Source Code.

<form class="form-signin" action="{% url "login" %}" method="post">
        <h2 class="form-signin-heading">Login</h2>
        <label for="recipient-name" class="control-label">Username:</label>
        <input type="text" class="form-control" name="username" placeholder="Username" required autofocus>
        <label for="recipient-name" class="control-label">Password:</label>
        <input type="password" class="form-control" name="password" placeholder="Password" required>
        <label for="recipient-name" class="control-label">Captcha:</label>
        {{ login_form.captcha }}
        <button class="btn btn-lg btn-primary btn-block" type="submit">Login</button>
        {% csrf_token %}

<!DOCTYPE html>
{% load staticfiles %}
<html lang="en">
    <meta charset="UTF-8">
            cursor: pointer;
    <form action="{% url "login" %}" method="post">
        <div><input type="text" name="username"></div>
        <div><input type="password" name="password"></div>
        <div><input type="text" name="code"><img src="{% url "create_captcha_code" %}" id="code"></div>
        <div>{{ msg }}</div>
        <div><input type="submit" value="Submit"></div>
        {% csrf_token %}
<script src="{% static "js/jquery-3.2.1.js" %}"></script>
    $("#code").click(function () {
        $(this)[0].src = $(this)[0].src + "?";

2.5 JQuery Source Code For Verification Code Refresh.

    // Add css style to captcha image.
            // The captcha image cursor is a pointer.
            "cursor": "pointer"

    // When the captcha image is clicked, use ajax to refresh the verification code.
    $(".captcha").click(function () {
        // The /captcha/refresh/ is the verification code refresh url.
                function (result) {
                    // Change the captcha image url to the server returned image url.
                    $(".captcha").attr("src", result["image_url"]);
                    // Set the captcha verification code to a hidden field.

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