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Todo list app using Flask | Python
  • Difficulty Level : Medium
  • Last Updated : 15 May, 2020

There are many frameworks that allow building your webpage using Python, like Django, flask, etc. Flask is a web application framework written in Python. Flask is based on WSGI(Web Server Gateway Interface) toolkit and Jinja2 template engine. Its modules and libraries that help the developer to write applications without writing the low-level codes such as protocols, thread management, etc.

In this article, we will learn how to make a todo list app using the Flask framework. In this app, you can add your todo items and mark them as complete or incomplete.


 pip install Flask

Basic setup :
Step 1: First make basic folders

mkdir app && cd app && mkdir static && mkdir templates

Step 2: Make some basic python files to write the code and name it as you desire.

Step 3: Run the below command to start the server

touch the app

Step 4: Change directory to app

 cd app

Step 5: create for database, for urls/views and __init__ file to package our app


Step 6: Goto templates/ directory and create index.html file

 cd templates && touch index.html 

Step 7: Goto static/ directory and create main.css

 cd static && touch main.css

Now, open the project folder using a text editor. The directory structure should look like this : file

from app import app
if __name__ == '__main__':

app/ file

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
import os
file_path = os.path.abspath(os.getcwd())+"/todo.db"
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///'+file_path
db = SQLAlchemy(app)
from app import routes

app/ file

from flask import render_template, request, redirect, url_for
from app import app
from app.models import Todo
from app import db
def index():
    incomplete = Todo.query.filter_by(complete=False).all()
    complete = Todo.query.filter_by(complete=True).all()
    return render_template('index.html', incomplete=incomplete, complete=complete)
@app.route('/add', methods=['POST'])
def add():
    todo = Todo(text=request.form['todoitem'], complete=False)
    return redirect(url_for('index'))
def complete(id):
    todo = Todo.query.filter_by(id=int(id)).first()
    todo.complete = True
    return redirect(url_for('index'))

app/ file

from app import db
class Todo(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    text = db.Column(db.String(200))
    complete = db.Column(db.Boolean)
    def __repr__(self):
        return self.text


<!DOCTYPE html> 
<html lang="en"
    <meta charset="UTF-8"
    <title>Todo App</title
    <link rel="stylesheet" type="text/css" href="{{url_for('static', filename='main.css')}}"
    <h1>Todo List</h1
    <div>Add a new todo item: 
        <form action="{{ url_for('add') }}" method="POST"
            <input type="text" name="todoitem"
            <input type="submit" value="Add Item" class="button"
        <h2>Incomplete Items</h2
            {% for todo in incomplete %} 
            <li style="font-size: 30pt" class='mark'>{{ todo.text }} <a href="{{ url_for('complete', }}">Mark As Complete</a></li
            {% endfor %}     
        <h2>Completed Items</h2
            {% for todo in complete %} 
            <li style="font-size: 30pt">{{ todo.text }}</li
            {% endfor %} 


    margin-top: 5px; 
.mark{font-size: 10px;} 

Run the todo app using the below command


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