Python Flask web application sample using MongoDB

Let us see how to set up a python flask web application that uses MongoDB back-end. In this topic, we will learn how to set up flask framework for the first time in your machine, how to run the flask applications, basic set up for your first HTML page and database actions like create a record, fetch data, update a record and delete (CRUD) from your flask application.

Different libraries are available in Python to connect to MongoDB. In this sample, PyMongo is used.
Contents
Install Python and setup Virtual Environment

Install Flask

Install PyMongo

Initial steps for Flask Web Apps
Setting up First page

MongoDB Database Setup

Fetch data from MongoDB and list

Insert new item to MongoDB
Update items - MongoDB

Delete an Item from MongoDB

Flask CRUD with MongoDB - Complete code

Other web app samples
Install Python and setup Virtual Environment

Download and install the latest version of python from Python Website.

Setting up virtual environment is not a must, but its is good to keep all your projects within a virtual environment. Here, we will proceed with a virtual environment.

For that, go to the command prompt and cd to the folder where you are going to keep your project.
Run command python -m venv CarSales to create a project folder CarSales and a virtual environment for it.
Activate the VE using command:

For Windows:

CarSales\Scripts\activate.bat

For Linux, macOS:

source CarSales /bin/activate

After VE activation, from cmd type cd CarSales to navigate to the project folder.
Install Flask

To install flask, run command pip install flask or pip3.9 install flask
If not working use commands:

For Windows:

py -3.9 -m pip install flask

For Linux, macOS:

python3.9 -m pip install flask

Run pip freeze or pip3.9 freeze to check if flask installed successfully. Should give an output like this.
```
click==8.1.3
colorama==0.4.4
Flask==2.1.2
itsdangerous==2.1.2
Jinja2==3.1.2
MarkupSafe==2.1.1
Werkzeug==2.1.2
```
Install PyMongo

For MongoDB connection we are going to use the PyMongo library. Install this using the command: pip install pymongo or py -3.9 -m pip install pymongo or python3.9 -m pip install pymongo
Initial steps for Flask Web Apps

Follow these basic steps to set up your first Flask web application.
Create a file named carsales.py (you can provide any name), inside CarSales folder and copy below code to it. carsales.py is going to contain your start-up code which is required to run your webapp. From command prompt navigate to CarSales folder and execute command py -3.9 -m carsales or python3.9 -m carsales or py carsales.py or python carsales.py depending on OS and Python version.
```
from flask import Flask

carsales = Flask(__name__)

if(__name__ == "__main__"):
    carsales.run()
```
This code imports Flask module and creates an object carsales of Flask class. Last 2 lines serves as the entry point of the app and starts the server. In cmd, we will see the below message.
```
    * Serving Flask app 'carsales' (lazy loading)
    * Environment: production
    Use a production WSGI server instead.
    * Debug mode: off
    * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
```
Copy the url http://127.0.0.1:5000/ to your browser and run. We will get the Not Found message as below.

This means that the Flask has handled the server set up and our application is ready. We will now have to set up our html pages and routing to handle page navigations.
Setting up First page

We are going to keep a list page as the first page of the application.
In Flask, all our HTML should be placed inside a folder named templates and static files like javascript or stylesheet should be placed inside static folder.So, create a folder structure as below within your application folder and add html file carslist.html inside templates folder.

Add below code to carslist.html. To handle routing for this page, modify carsales.py as below. This code imports render_template module and sets up the default route.
Copied

from flask import Flask, render_template carsales = Flask(__name__) @carsales.route("/") #For default route def main(): return render_template("carslist.html") if(__name__ == "__main__"): carsales.run()
Copied

<!DOCTYPE html> <html lang="en-US" dir="ltr"> <head> <title>Cars List</title> </head> <body> <h2>Cars List</h2> </body>
In command prompt. click Ctrl + C to stop the application and run command py -3.9 -m carsales or python3.9 -m carsales or py carsales or python carsales (Varies depending on OS and the python version used). This process is to be done each time we make any changes and want to reload the page. Some times, after stopping flask application from command prompt, just reloading the html will not give you the desired output. If any such issues are faced, close the web page and reopen.

Database Setup

We will use the PyMongo adapter to create database and a table and insert data to it.
Create a file named mongodbData.py in the same code folder and paste the below code in it.
Run this file using command py mongodbData.py or python mongodbData.py or py -3.9 -m mongodbData or python3.9 -m mongodbData.py

This set of code connects to the local MongoDB client and then creates a database and a table in it. You should have MongoDB installed locally in your machine or use a valid server url in the below code.
Then we are inserting five records to the table.

import pymongo

carsalesClient = pymongo.MongoClient("mongodb://localhost:27017/")
carsalesDB = carsalesClient["CarSales"]
tblCars = carsalesDB["TblCars"]

carslist = [
  { "ID": 1, "Name": "Toyota Camry", "Year": 2018, "Price": 2000 },
  { "ID": 2, "Name": "Honda Civic", "Year": 2019, "Price": 2200 },
  { "ID": 3, "Name": "Chevrolet Silverado", "Year": 2017, "Price": 1800 },
  { "ID": 4, "Name": "Ford F-150", "Year": 2020, "Price": 2500 },
  { "ID": 5, "Name": "Nissan Altima", "Year": 2021, "Price": 3000 }
]

tbl = tblCars.insert_many(carslist)
print(tbl.inserted_ids)

Fetch data from MongoDB and list

carslist.html is going to hold the list of cars available for sale. To list the items, add below code in body of html and modify carsales.py main method as below. Also import pymongo. In python file, we are reading data from MongoDB database CarSales using pymongo built-in functions as shown below and pass it to html as a parameter. In html, we are looping through the items and list it as table rows.

from flask import Flask, render_template
import pymongo

carsales = Flask(__name__)

def connectDB():
    carsalesClient = pymongo.MongoClient("mongodb://localhost:27017/")
    carsalesDB = carsalesClient["CarSales"]
    return carsalesDB


@carsales.route("/")
def main():
    cars = []
    carsalesDB = connectDB()
    tblCars = carsalesDB["TblCars"]

    for car in tblCars.find():
        cars.append({"id": car["ID"], "name": car["Name"], "year": car["Year"], "price": car["Price"]})
    return render_template("carslist.html", cars = cars)

if(__name__ == "__main__"):
    carsales.run()

<table class="table">
    <thead>
        <tr>
        <th scope="col">Id</th>
        <th scope="col">Name</th>
        <th scope="col">Year</th>
        <th scope="col">Price</th>
        </tr>
    </thead>
    <tbody>
        {% for car in cars %}
            <tr>
                <td>{{ car.id }}</th>
                <td>{{ car.name }}</td>
                <td>{{ car.year }}</td>
                <td>{{ car.price }}</td>
            </tr>
        {% endfor %}
    </tbody>
</table>

For styling we will use Bootstrap 5. Add below 2 lines inside head of html.


    <link rel="stylesheet" crossorigin="anonymous"
	href="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/css/bootstrap.min.css" >
    
	<script crossorigin="anonymous"
	src="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/js/bootstrap.bundle.min.js" >
	</script>

On rerun, we will get below output window.

Insert new item to MongoDB

Add a new button in the carslist.html above the table.

    <a class="btn btn-primary" href="addcar">Add New Car</a>

Add new html file, addcar.html and place below code. Add below code in caresales.py as the second route below main method.

@carsales.route("/addcar", methods = ['GET','POST'])
def addcar():
    if request.method == 'GET':
        return render_template("addcar.html")
    if request.method == 'POST':
        id = int(request.form["id"])
        name = request.form["name"]
        year = int(request.form["year"])
        price = float(request.form["price"])
        
        carsalesDB = connectDB()
        tblCars = carsalesDB["TblCars"]
        tblCars.insert_one( { "ID": id, "Name": name, "Year": year, "Price": price } )
        return redirect('/')

<!DOCTYPE html>
<html lang="en-US" dir="ltr">
<head>
    <title>Car Details</title>
    
    <link rel="stylesheet" crossorigin="anonymous"
	href="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/css/bootstrap.min.css" >
    
	<script crossorigin="anonymous"
	src="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/js/bootstrap.bundle.min.js" >
	</script>

</head>

<body>
    <h2>Car Details</h2>

    <form action="" method = "POST">
        <div class="form-group row">
          <label for="id">Id</label>
          <input type="text" class="form-control" name="id" id="id">
        </div>
        <div class="form-group row">
            <label for="name">Maker and Model</label>
            <input type="text" class="form-control" name="name" id="name">
        </div>
        <div class="form-group row">
            <label for="year">Make Year</label>
            <input type="text" class="form-control" name="year" id="year">
        </div>
        <div class="form-group row">
            <label for="price">Sell Price</label>
            <input type="text" class="form-control" name="price" id="price">
        </div>
        <button type="btnAdd" class="btn btn-primary">Submit</button>
        <a href="/" class="btn btn-primary">Cancel</a>
      </form>
</body>

Now we have to import request and redirect. For that, change first line of caresales.py as below.

from flask import Flask, render_template, request, redirect

In the python code, we are defining a new route for addcar. We are using the same method for GET and POST. GET is just rendering addcar.html. In POST, we are reading data from form controls and save data to table and then redirect to list page.

In HTML page, we are defining a form with 4 text boxes. Each has a name provided. This name is used in the python file while reading data from controls.
On rerun, we can navigate to Create page as below and add new Car.

Update items - MongoDB

For update and delete add 2 links in the carslist.html page as below.

<table class="table">
    <thead>
        <tr>
        <th scope="col">Id</th>
        <th scope="col">Name</th>
        <th scope="col">Year</th>
        <th scope="col">Price</th>
        <th scope="col">Edit</th>
        <th scope="col">Delete</th>
        </tr>
    </thead>
    <tbody>
        {% for car in cars %}
            <tr>
                <td>{{ car.id }}</th>
                <td>{{ car.name }}</td>
                <td>{{ car.year }}</td>
                <td>{{ car.price }}</td>
                <td><a href='updatecar/{{ car.id }}'>Edit</a></td>
                <td><a href='deletecar/{{ car.id }}'>Delete</a></td>
            </tr>
        {% endfor %}
    </tbody>
</table>

First, in addcar.html, in order to populate the values, use the value attribute and bind the car object values as in html provided below.

Then, in carsales.py, add new updatecar route. Use the GET to fetch the details of the selected item and bind to the html. In POST, we are calling the update_one method to update records based on the seleted ID.

Note: Disable the ID textbox to not make changes to ID. Here we are not doing it and if ID is changed no update will happen.

@carsales.route('/updatecar/<int:id>',methods = ['GET','POST'])
def updatecar(id):
    cr = []
    carsalesDB = connectDB()
    tblCars = carsalesDB["TblCars"]

    if request.method == 'GET':
        for car in tblCars.find( { "ID": id } ):
            cr.append({"id": car["ID"], "name": car["Name"], "year": car["Year"], "price": car["Price"]})
        return render_template("addcar.html", car = cr[0])
    if request.method == 'POST':
        name = str(request.form["name"])
        year = int(request.form["year"])
        price = float(request.form["price"])
        condition = { "ID": id }
        updatedval = { "$set": { "Name": name, "Year": year, "Price": price } }
        tblCars.update_one(condition, updatedval)
        return redirect('/')

<!DOCTYPE html>
<html lang="en-US" dir="ltr">
<head>
    <title>Car Details</title>
    
    <link rel="stylesheet" crossorigin="anonymous"
	href="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/css/bootstrap.min.css" >
    
	<script crossorigin="anonymous"
	src="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/js/bootstrap.bundle.min.js" >
	</script>

</head>

<body>
    <h2>Car Details</h2>

    <form action="" method = "POST">
        <div class="form-group row">
          <label for="id">Id</label>
          <input type="text" class="form-control" name="id" id="id" value="{{car.id}}">
        </div>
        <div class="form-group row">
            <label for="name">Maker and Model</label>
            <input type="text" class="form-control" name="name" id="name" value="{{car.name}}">
        </div>
        <div class="form-group row">
            <label for="year">Make Year</label>
            <input type="text" class="form-control" name="year" id="year" value="{{car.year}}">
        </div>
        <div class="form-group row">
            <label for="price">Sell Price</label>
            <input type="text" class="form-control" name="price" id="price" value="{{car.price}}">
        </div>
        <button type="btnAdd" class="btn btn-primary">Submit</button>
        <a href="/" class="btn btn-primary">Cancel</a>
      </form>
</body>

After the above changes, update will work, but create will throw an error. To fix this, change the render_template line of addcar as below.

return render_template("addcar.html", car = {})

We are binding an empty car object to make it working.

Delete an Item from MongoDB

For delete, add a new route deletecar and call delete_one method as below.

@carsales.route('/deletecar/<int:id>')
def deletecar(id):
    carsalesDB = connectDB()
    tblCars = carsalesDB["TblCars"]
    tblCars.delete_one({ "ID": id })
    return redirect('/')

Flask CRUD with MongoDB database - Complete code

Complete code is placed below.

from flask import Flask, render_template, request, redirect
import pymongo

carsales = Flask(__name__)

def connectDB():
    carsalesClient = pymongo.MongoClient("mongodb://localhost:27017/")
    carsalesDB = carsalesClient["CarSales"]
    return carsalesDB
	

@carsales.route("/")
def main():
    cars = []
    carsalesDB = connectDB()
    tblCars = carsalesDB["TblCars"]

    for car in tblCars.find():
        cars.append({"id": car["ID"], "name": car["Name"], "year": car["Year"], "price": car["Price"]})
    return render_template("carslist.html", cars = cars)

@carsales.route("/addcar", methods = ['GET','POST'])
def addcar():
    if request.method == 'GET':
        return render_template("addcar.html", car = {})
    if request.method == 'POST':
        id = int(request.form["id"])
        name = request.form["name"]
        year = int(request.form["year"])
        price = float(request.form["price"])
        
        carsalesDB = connectDB()
        tblCars = carsalesDB["TblCars"]
        tblCars.insert_one( { "ID": id, "Name": name, "Year": year, "Price": price } )
        return redirect('/')

@carsales.route('/updatecar/<int:id>',methods = ['GET','POST'])
def updatecar(id):
    cr = []
    carsalesDB = connectDB()
    tblCars = carsalesDB["TblCars"]

    if request.method == 'GET':
        for car in tblCars.find( { "ID": id } ):
            cr.append({"id": car["ID"], "name": car["Name"], "year": car["Year"], "price": car["Price"]})
        return render_template("addcar.html", car = cr[0])
    if request.method == 'POST':
        name = str(request.form["name"])
        year = int(request.form["year"])
        price = float(request.form["price"])
        condition = { "ID": id }
        updatedval = { "$set": { "Name": name, "Year": year, "Price": price } }
        tblCars.update_one(condition, updatedval)
        return redirect('/')

@carsales.route('/deletecar/<int:id>')
def deletecar(id):
    carsalesDB = connectDB()
    tblCars = carsalesDB["TblCars"]
    tblCars.delete_one({ "ID": id })
    return redirect('/')

if(__name__ == "__main__"):
    carsales.run()

<!DOCTYPE html>
<html lang="en-US" dir="ltr">
<head>
    <title>Cars List</title>
    
    <link rel="stylesheet" crossorigin="anonymous"
	href="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/css/bootstrap.min.css" >
    
	<script crossorigin="anonymous"
	src="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/js/bootstrap.bundle.min.js" >
	</script>

</head>

<body>
    <h2>Cars List</h2>
    <a class="btn btn-primary" href="addcar">Add New Car</a>
    <table class="table">
        <thead>
            <tr>
            <th scope="col">Id</th>
            <th scope="col">Name</th>
            <th scope="col">Year</th>
            <th scope="col">Price</th>
            <th scope="col">Edit</th>
            <th scope="col">Delete</th>
            </tr>
        </thead>
        <tbody>
            {% for car in cars %}
                <tr>
                    <td>{{ car.id }}</th>
                    <td>{{ car.name }}</td>
                    <td>{{ car.year }}</td>
                    <td>{{ car.price }}</td>
                    <td><a href='updatecar/{{ car.id }}'>Edit</a></td>
                    <td><a href='deletecar/{{ car.id }}'>Delete</a></td>
                </tr>
            {% endfor %}
        </tbody>
    </table>
</body>

<!DOCTYPE html>
<html lang="en-US" dir="ltr">
<head>
    <title>Car Details</title>
    
    <link rel="stylesheet" crossorigin="anonymous"
	href="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/css/bootstrap.min.css" >
    
	<script crossorigin="anonymous"
	src="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/js/bootstrap.bundle.min.js" >
	</script>

</head>

<body>
    <h2>Car Details</h2>

    <form action="" method = "POST">
        <div class="form-group row">
          <label for="id">Id</label>
          <input type="text" class="form-control" name="id" id="id" value="{{car.id}}">
        </div>
        <div class="form-group row">
            <label for="name">Maker and Model</label>
            <input type="text" class="form-control" name="name" id="name" value="{{car.name}}">
        </div>
        <div class="form-group row">
            <label for="year">Make Year</label>
            <input type="text" class="form-control" name="year" id="year" value="{{car.year}}">
        </div>
        <div class="form-group row">
            <label for="price">Sell Price</label>
            <input type="text" class="form-control" name="price" id="price" value="{{car.price}}">
        </div>
        <button type="btnAdd" class="btn btn-primary">Submit</button>
        <a href="/" class="btn btn-primary">Cancel</a>
      </form>
</body>

Other web app samples

Crud Samples implemented using different frameworks and databases.

Flask

Flask CRUD with JSON

Flask CRUD with SQL Server

Flask CRUD with MySQL

Flask Web App Sample using MongoDB

Flask CRUD with Oracle

Flask CRUD with PostgreSQL

Flask Web App Sample using MariaDB

Flask Web App Sample using Firebase DB

Django

Django CRUD with JSON

Django CRUD with SQL Server

Django CRUD with MySQL

Django Web App Sample using MongoDB

Django CRUD with Oracle

Django CRUD with PostgreSQL

Django Web App Sample using MariaDB

Django Web App Sample using Firebase DB

CherryPy

CherryPy CRUD with SQL Server

CherryPy Web App Sample using MongoDB

CherryPy CRUD with Oracle

CherryPy CRUD with JSON

CherryPy Web App Sample using Firebase DB

CherryPy CRUD with MySQL

CherryPy Web App Sample using MariaDB

CherryPy CRUD with PostgreSQL

Python Flask web application sample using MongoDB

Contents

Install Python and setup Virtual Environment

Install Flask

Install PyMongo

Initial steps for Flask Web Apps

Setting up First page

Database Setup

Fetch data from MongoDB and list

Insert new item to MongoDB

Update items - MongoDB

Delete an Item from MongoDB

Flask CRUD with MongoDB database - Complete code

Other web app samples

Flask

Django

CherryPy