---
title: "Create a simple flask app with aider"
description: "In this chat transcript, the user asks to make a simple flask app with various endpoints."
type: skill
canonical_url: https://claudary.paisolsolutions.com/skills/hello-world-flask
source: "Claudary"
difficulty: intermediate
author: "Claude Code Knowledge Pack"
date: 2026-07-10T11:25:09.937Z
license: CC-BY-4.0
attribution: "Create a simple flask app with aider — Claudary (https://claudary.paisolsolutions.com/skills/hello-world-flask)"
---

# Create a simple flask app with aider
In this chat transcript, the user asks to make a simple flask app with various endpoints.

## Overview

---
parent: Example chat transcripts
nav_order: 1
---

# Create a simple flask app with aider

In this chat transcript, the user asks to make a simple flask app with various endpoints.

<div class="chat-transcript" markdown="1">

> $ aider app.py  
> Creating empty file app.py  
> Added app.py to the chat  

#### make a flask app with a /hello endpoint that returns hello world  

To create a Flask app with a `/hello` endpoint that returns "Hello, World!", we need to install Flask, import it, create an app instance, and define a route for the `/hello` endpoint. Here's how to update the `app.py` file:

```python
app.py
<<<<<<< ORIGINAL

=======
from flask import Flask

app = Flask(__name__)

@app.route('/hello')
def hello():
    return "Hello, World!"

if __name__ == '__main__':
    app.run()
>>>>>>> UPDATED
```

Make sure to install Flask in your project environment using `pip install flask` before running the app.

> Applied edit to app.py  
> Commit 414c394 aider: Added a `/hello` endpoint that returns "Hello, World!" to the Flask app.  

</div>
<div class="chat-transcript" markdown="1">
#### add an endpoint like /add/3/5 which returns the sum of the 2 numbers  

To add an endpoint like `/add/3/5` that returns the sum of the two numbers, you can create a new route with two URL parameters. Update the `app.py` file as follows:

```python
app.py
<<<<<<< ORIGINAL
@app.route('/hello')
def hello():
    return "Hello, World!"
=======
@app.route('/add/<int:num1>/<int:num2>')
def add(num1, num2):
    return str(num1 + num2)

@app.route('/hello')
def hello():
    return "Hello, World!"
>>>>>>> UPDATED
```

Now, when you visit `/add/3/5`, it will return the sum of the two numbers, which is `8`.

> Applied edit to app.py  
> Commit 0872c51 aider: Added an endpoint `/add/<int:num1>/<int:num2>` that returns the sum of the two numbers.  

</div>
<div class="chat-transcript" markdown="1">
#### add /fibonacci/X  

To add a `/fibonacci/X` endpoint that returns the Xth number in the Fibonacci sequence, you can create a new route with a URL parameter for X and a function to calculate the Fibonacci number. Update the `app.py` file as follows:

```python
app.py
<<<<<<< ORIGINAL
@app.route('/hello')
def hello():
    return "Hello, World!"
=======
def fibonacci(n):
    if n <= 0:
        return "Invalid input. Please enter a positive integer."
    elif n == 1:
        return 0
    elif n == 2:
        return 1
    else:
        a, b = 0, 1
        for _ in range(n - 2):
            a, b = b, a + b
        return b

@app.route('/fibonacci/<int:x>')
def fibonacci_x(x):
    return str(fibonacci(x))

@app.route('/hello')
def hello():
    return "Hello, World!"
>>>>>>> UPDATED
```

Now, when you visit `/fibonacci/X`, it will return the Xth number in the Fibonacci sequence. For example, `/fibonacci/5` will return `3`.

> Applied edit to app.py  
> Commit 163fba8 aider: Added a `/fibonacci/X` endpoint that returns the Xth number in the Fibonacci sequence.  

</div>
<div class="chat-transcript" markdown="1">
#### remove the hello endpoint  

To remove the `/hello` endpoint, you can simply delete the corresponding route and function in the `app.py` file. Here's the update:

```python
app.py
<<<<<<< ORIGINAL
@app.route('/hello')
def hello():
    return "Hello, World!"
=======
>>>>>>> UPDATED
```

Now, the `/hello` endpoint has been removed from the Flask app.

> Applied edit to app.py  
> Commit eab6620 aider: Removed the `/hello` endpoint from the Flask app.  


</div>

---

Source: [Claudary](https://claudary.paisolsolutions.com/skills/hello-world-flask) · https://claudary.paisolsolutions.com