How to create a website in Python - Python Flask tutorial - First basic website

Python is a very popular language right now. Many big companies are using it. Python is used in most of the fields. You can create softwares, basic games as well as websites in Python. In web development, Python's libraries are considered very good for making backends. Even companies like Netflix use Python in their backend.

Basically, there are two main Python libraries, with which you can learn wen development and create a backend for your site. First is Flask, the other is Django. Flask is a little simple.

Here I will show how you can make your first Python website with Flask...

Process

• Install the Flask library, by running the command pip install flask in your terminal.
• Then you are ready for making your first Flask App
• To get your first app, Create a new file and paste the below code. This is the basic structure of a Flask application.

The Code

Congratulations, you have made your first Flask app.

Now open the terminal and run the command flask run

import sys
from PyQt5.QtCore import *
from PyQt5.QtWidgets import *

class MainWindow(QMainWindow):
    def __init__(self):
        # Main Window
        super(MainWindow, self).__init__()
        self.showMaximized()

app = QApplication(sys.argv)
QApplication.setApplicationName("Browser")
window = MainWindow()
app.exec_()

PyQt5 Basic code

import sys
from PyQt5.QtCore import *
from PyQt5.QtWidgets import *

class MainWindow(QMainWindow):
    def __init__(self):
        # Main Window
        super(MainWindow, self).__init__()
        self.showMaximized()

app = QApplication(sys.argv)
QApplication.setApplicationName("Browser")
window = MainWindow()
app.exec_()

PyQt5 Browser code using QtWebEngine

import sys
from PyQt5.QtCore import *
from PyQt5.QtWidgets import *
from PyQt5.QtWebEngineWidgets import *

class MainWindow(QMainWindow):
    def __init__(self):
        # Main Window
        super(MainWindow, self).__init__()
        self.browser = QWebEngineView()
        self.browser.setUrl(QUrl('https://google.com'))
        self.setCentralWidget(self.browser)
        self.showMaximized()

        # nav bar
        navBar = QToolBar()
        self.addToolBar(navBar)

        backBtn = QAction("Back", self)     # back Button
        backBtn.triggered.connect(self.browser.back)
        navBar.addAction(backBtn)

        forwardBtn = QAction("Forward", self)   # forward Button
        forwardBtn.triggered.connect(self.browser.forward)
        navBar.addAction(forwardBtn)

        relBtn = QAction("Reload", self)    # Reload Button
        relBtn.triggered.connect(self.browser.reload)
        navBar.addAction(relBtn)

app = QApplication(sys.argv)
QApplication.setApplicationName("Browser")
window = MainWindow()
app.exec_()

# program 1: that finds whether the entered no. is 1/2/3 digits
a = int(input("Enter a no.: "))

if a < 0 or a > 999:
    print("Please enter a no. in range 1 to 999")
else:
    if a<10:
        print("The no. is a 1-digit number")
    elif a<100:
        print("The no. is a 2-digit number")
    elif a<1000:
        print("The no. is a 3-digit number")
        
        
# program 2: ask user to input numbers until entered 'done', then print the sum of all entered numbers.
c=0

while True:
    a = input("Enter a no.: ")
    if a == 'done':
        print(c)
        break
    elif a != 'done' and a.isnumeric() != True:
        print("invalid key command")
        break
    else:
        c += int(a)


# Program 3: ask the day no. and the first day of a year. Then print the day on the day no. provided
_day = int(input("Enter the day no. from 2 to 365: "))
day_n = str(input("Enter the first day of that year: "))
day_list = ["sunday", "monday", "tuesday", "wednesday", "thursday", "friday", "saturday"]

if day_n in day_list:
    a = _day % 7
    for i in range(0, 7):
        day_list_i = day_list[i]
        if day_list_i == day_n:
            for j in range (i, i+7):
                day_var = day_list[(a+j)%7]
            print(day_var)
else:
    print("Please don't try to fool the program :')")


# Program 4: miles to k.m. conversion table

print("miles\t|\tk.m.")
for data in range(1, 11):
    print(f"{data}\t|\t{data * 1.609}")
    

# Program 5: Print the stats of entered string (like total lowercase/uppercase characters adn no. of alphabets and numbers)
l = input("Enter a string: ")
lowercount = uppercount = alphabet = numbers = 0
for a in l:
    if a.islower():
        lowercount += 1
    if a.isupper():
        uppercount += 1
    if a.isalpha():
        alphabet += 1
    if a.isnumeric():
        numbers += 1

print(f"Lowercase: {lowercount}\nUppercase: {uppercount}\nAlphabets: {alphabet}\nNumbers: {numbers}")

    
        
// The code. Just copy from here. Replace "<!--" by "<?"
<?php 
session_start();

<!-- First We will see user authentication with login. -->

// initializing variables
$username = "";
$email = "";
$user_id = "";
$errors = array(); 

$db = mysqli_connect('localhost', 'root', '', 'test');

if (isset($_POST['reg_user'])) {
  $username = mysqli_real_escape_string($db, $_POST['username']);
  $email = mysqli_real_escape_string($db, $_POST['email']);
  $password_1 = mysqli_real_escape_string($db, $_POST['password_1']);
  $password_2 = mysqli_real_escape_string($db, $_POST['password_2']);

  // form validation: ensure that the form is correctly filled ...
  // by adding (array_push()) corresponding error unto $errors array
  if (empty($username)) { array_push($errors, "Username is required"); }
  if (empty($email)) { array_push($errors, "Email is required"); }
  if (empty($password_1)) { array_push($errors, "Password is required"); }
  if ($password_1 != $password_2) {
	array_push($errors, "The two passwords do not match");
  }

  // first check the database to make sure 
  // a user does not already exist with the same username and/or email
  $user_check_query = "SELECT * FROM users WHERE username='$username' OR email='$email' LIMIT 1";
  $result = mysqli_query($db, $user_check_query);
  $user = mysqli_fetch_assoc($result);
  
  if ($user) { // if user exists
    if ($user['username'] === $username) {
      array_push($errors, "Username already exists");
    }

    if ($user['email'] === $email) {
      array_push($errors, "email already exists");
    }
  }

  // Finally, register user if there are no errors in the form
  if (count($errors) == 0) {
  	$password = md5($password_1);

  	$query = "INSERT INTO users (username, email, password) 
  			  VALUES('$username', '$email', '$password')";
  	mysqli_query($db, $query);
  	$_SESSION['username'] = $username;
  	$_SESSION['success'] = "You are now logged in";
  	header('location: main.php');
  }
}


// LOGIN USER
if (isset($_POST['login_user'])) {
    $username = mysqli_real_escape_string($db, $_POST['username']);
    $password = mysqli_real_escape_string($db, $_POST['password']);
  
    if (empty($username)) {
        array_push($errors, "Username is required");
    }
    if (empty($password)) {
        array_push($errors, "Password is required");
    }
  
    if (count($errors) == 0) {
        $password = md5($password);
        $query = "SELECT * FROM users WHERE username='$username' AND password='$password'";
        $results = mysqli_query($db, $query);

        if (mysqli_num_rows($results) == 1) {
          $_SESSION['loggedin'] = true;
          $_SESSION['username'] = $username;
          $_SESSION['success'] = "You are now logged in";
          header('location: main.php');
        }else {
            array_push($errors, "Wrong username/password combination");
        }
    }
}


if (!$db) {
  die("Error connecting to database: " . mysqli_connect_error($db));
  exit();
}


if (isset($_SESSION['loggedin'])) {
  $user_id = $_SESSION['username'];
}

if (isset($_SESSION['success'])) {
// if user clicks like or dislike button
  if (isset($_POST['action'])) {
    $post_id = $_POST['post_id'];
    $action = $_POST['action'];
    switch ($action) {
      case 'like':
          $sql="INSERT INTO rating_info VALUES ('$user_id', $post_id, 'like')";
            $sql1 = "SELECT * FROM rating_info WHERE user_id='$user_id' AND post_id=$post_id AND rating_action='dislike'";
            $result = mysqli_query($db, $sql1);
            if (mysqli_num_rows($result) > 0) {
              $sql = "UPDATE rating_info SET rating_action='like' WHERE user_id='$user_id' AND post_id=$post_id AND rating_action='dislike'";
            }
          break;
      case 'dislike':
            $sql="INSERT INTO rating_info VALUES ('$user_id', $post_id, 'dislike')";
            $sql1 = "SELECT * FROM rating_info WHERE user_id='$user_id' AND post_id=$post_id AND rating_action='like'";
            $result = mysqli_query($db, $sql1);
            if (mysqli_num_rows($result) > 0) {
              $sql = "UPDATE rating_info SET rating_action='dislike' WHERE user_id='$user_id' AND post_id=$post_id AND rating_action='like'";
            }
          break;
      case 'unlike':
            $sql="DELETE FROM rating_info WHERE user_id='$user_id' AND post_id=$post_id";
          break;
      case 'undislike':
            $sql="DELETE FROM rating_info WHERE user_id='$user_id' AND post_id=$post_id";
        break;
      default:
        break;
    }

    // execute query to effect changes in the database ...
    mysqli_query($db, $sql);
    echo getRating($post_id);
    exit(0);
  }
}

// Get total number of likes for a particular post
function getLikes($id)
{
  global $db;
  $sql = "SELECT COUNT(*) FROM rating_info 
  		  WHERE post_id = $id AND rating_action='like'";
  $rs = mysqli_query($db, $sql);
  $result = mysqli_fetch_array($rs);
  return $result[0];
}

// Get total number of dislikes for a particular post
function getDislikes($id)
{
  global $db;
  $sql = "SELECT COUNT(*) FROM rating_info 
  		  WHERE post_id = $id AND rating_action='dislike'";
  $rs = mysqli_query($db, $sql);
  $result = mysqli_fetch_array($rs);
  return $result[0];
}

// Get total number of likes and dislikes for a particular post
function getRating($id)
{
  global $db;
  $rating = array();
  $likes_query = "SELECT COUNT(*) FROM rating_info WHERE post_id = $id AND rating_action='like'";
  $dislikes_query = "SELECT COUNT(*) FROM rating_info 
		  			WHERE post_id = $id AND rating_action='dislike'";
  $likes_rs = mysqli_query($db, $likes_query);
  $dislikes_rs = mysqli_query($db, $dislikes_query);
  $likes = mysqli_fetch_array($likes_rs);
  $dislikes = mysqli_fetch_array($dislikes_rs);
  $rating = [
  	'likes' => $likes[0],
  	'dislikes' => $dislikes[0]
  ];
  return json_encode($rating);
}

// Check if user already likes post or not
function userLiked($post_id)
{
  global $db;
  global $user_id;
  $sql = "SELECT * FROM rating_info WHERE user_id='$user_id' AND post_id=$post_id AND rating_action='like'";
  $result = mysqli_query($db, $sql);
  if (mysqli_num_rows($result) > 0) {
  	return true;
  }else{
  	return false;
  }
}

// Check if user already dislikes post or not
function userDisliked($post_id)
{
  global $db;
  global $user_id;
  $sql = "SELECT * FROM rating_info WHERE user_id='$user_id' AND post_id=$post_id AND rating_action='dislike'";
  $result = mysqli_query($db, $sql);
  if (mysqli_num_rows($result) > 0) {
  	return true;
  }else{
  	return false;
  }
}

$sql = "SELECT * FROM posts";
$result = mysqli_query($db, $sql);
// fetch all posts from database
// return them as an associative array called $posts
$posts = mysqli_fetch_all($result, MYSQLI_ASSOC);

?>
<!--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>php tutorial - like dislike system</title>
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.4.1/css/bootstrap.min.css">
  <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.4.1/js/bootstrap.min.js"></script>
  <link rel="stylesheet" href="css/style.css">
</head>
<body>
  <div class="container">
<!--php if (isset($_SESSION['success'])) : ?-->
   <!--php foreach ($posts as $post): ?-->
   	<div class="post">
    <a class="title tahoma" href="item.php">
      <!--php echo $post['title']; ?-->
    </a>
    <br>
      <div class="post-info">
      	<i <?php if (userLiked($post['id'])): ?>
      		  class="fa fa-thumbs-up like-btn"
      	  <!--php else: ?-->
      		  class="fa fa-thumbs-o-up like-btn"
      	  <!--php endif ?-->
      	  data-id="<!--php echo $post['id'] ?-->"></i>
      	<span class="likes"><!--php echo getLikes($post['id']); ?--></span>
      	
      	&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

      	<i 
      	  <?php if (userDisliked($post['id'])): ?>
      		  class="fa fa-thumbs-down dislike-btn"
      	  <!--php else: ?-->
      		  class="fa fa-thumbs-o-down dislike-btn"
      	  <!--php endif ?-->
      	  data-id="<!--php echo $post['id'] ?-->"></i>
      	<span class="dislikes"><!--php echo getDislikes($post['id']); ?--></span>
      </div>
   	</div>
   <!--php endforeach ?-->

   <!--php else : ?-->
    <!--php foreach ($posts as $post): ?-->
   	<div class="post">
    <a class="title tahoma" href="item.php">
      <!--php echo $post['title']; ?-->
    </a>
    <br>
      <div class="post-info">
      	<a onclick="nfunc()"><i class="fa fa-thumbs-o-up like-btn" data-id="<?php echo $post['id'] ?>"></i></a>
      	<span class="likes"><!--php echo getLikes($post['id']); ?--></span>
      	
      	&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

      	<a onclick="nfunc()"><i class="fa fa-thumbs-o-down dislike-btn"
      	  data-id="<?php echo $post['id'] ?>"></i></a>
      	<span class="dislikes"><!--php echo getDislikes($post['id']); ?--></span>
      </div>
   	</div>
   <!--php endforeach ?-->
   <!--php endif ?-->
  </div>
    </div>
</body>
<script>
  $(document).ready(function(){

// if the user clicks on the like button ...
$('.like-btn').on('click', function(){
  var post_id = $(this).data('id');
  $clicked_btn = $(this);
  if ($clicked_btn.hasClass('fa-thumbs-o-up')) {
  	action = 'like';
  } else if($clicked_btn.hasClass('fa-thumbs-up')){
  	action = 'unlike';
  }
  $.ajax({
  	url: 'index.php',
  	type: 'post',
  	data: {
  		'action': action,
  		'post_id': post_id
  	},
  	success: function(data){
  		res = JSON.parse(data);
  		if (action == "like") {
  			$clicked_btn.removeClass('fa-thumbs-o-up');
  			$clicked_btn.addClass('fa-thumbs-up');
  		} else if(action == "unlike") {
  			$clicked_btn.removeClass('fa-thumbs-up');
  			$clicked_btn.addClass('fa-thumbs-o-up');
  		}
  		// display the number of likes and dislikes
  		$clicked_btn.siblings('span.likes').text(res.likes);
  		$clicked_btn.siblings('span.dislikes').text(res.dislikes);

  		// change button styling of the other button if user is reacting the second time to post
  		$clicked_btn.siblings('i.fa-thumbs-down').removeClass('fa-thumbs-down').addClass('fa-thumbs-o-down');
  	}
  });		

});

// if the user clicks on the dislike button ...
$('.dislike-btn').on('click', function(){
  var post_id = $(this).data('id');
  $clicked_btn = $(this);
  if ($clicked_btn.hasClass('fa-thumbs-o-down')) {
  	action = 'dislike';
  } else if($clicked_btn.hasClass('fa-thumbs-down')){
  	action = 'undislike';
  }
  $.ajax({
  	url: 'index.php',
  	type: 'post',
  	data: {
  		'action': action,
  		'post_id': post_id
  	},
  	success: function(data){
  		res = JSON.parse(data);
  		if (action == "dislike") {
  			$clicked_btn.removeClass('fa-thumbs-o-down');
  			$clicked_btn.addClass('fa-thumbs-down');
  		} else if(action == "undislike") {
  			$clicked_btn.removeClass('fa-thumbs-down');
  			$clicked_btn.addClass('fa-thumbs-o-down');
  		}
  		// display the number of likes and dislikes
  		$clicked_btn.siblings('span.likes').text(res.likes);
  		$clicked_btn.siblings('span.dislikes').text(res.dislikes);
  		
  		// change button styling of the other button if user is reacting the second time to post
  		$clicked_btn.siblings('i.fa-thumbs-up').removeClass('fa-thumbs-up').addClass('fa-thumbs-o-up');
  	}
  });	

});

});

</script>
</html>
        
    

Then Bye Bye!
Thanks for reading... :)
See you!

Extra Reading:

A notification is about something (object = event, friendship..) being changed (verb = added, requested..) by someone (actor) and reported to the user (subject). Here is a normalized data structure (though I've used MongoDB). You need to notify certain users about changes. So it's per-user notifications.. meaning that if there were 100 users involved, you generate 100 notifications.

(Add time fields where you see fit)

This is basically for grouping changes per object, so that you could say "You have 3 friend requests". And grouping per actor is useful, so that you could say "User James Bond made changes in your bed". This also gives ability to translate and count notifications as you like.

But, since object is just an ID, you would need to get all extra info about object you want with separate calls, unless object actually changes and you want to show that history (so for example "user changed title of event to ...")