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Introduction

In this quickstart tutorial, we will explore how to use Flask with Upstash Redis to build a simple web application that increments a counter each time a user accesses the homepage.

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Environment Setup

First, install Flask and the Upstash Redis client for Python. 
pip install flask
pip install upstash-redis

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Database Setup

Create a Redis database using Upstash Console or Upstash CLI and export the UPSTASH_REDIS_REST_URL and UPSTASH_REDIS_REST_TOKEN to your environment. 
export UPSTASH_REDIS_REST_URL=<YOUR_URL>
export UPSTASH_REDIS_REST_TOKEN=<YOUR_TOKEN>
You can also use python-dotenv to load environment variables from your .env file.

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Application Setup

Create app.py:
app.py
from flask import Flask
from upstash_redis import Redis

app = Flask(__name__)

redis = Redis.from_env()

@app.route('/')
def index():
    count = redis.incr('counter')
    return f'Page visited {count} times.'

if __name__ == '__main__':
    app.run(debug=True)

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Running the Application

Run the Flask app locally: 
python app.py
Visit http://127.0.0.1:5000/ in your browser, and you will see the counter increment with each refresh. Code Breakdown
  1. Redis Setup: We first import Flask and the Upstash Redis client. Using Redis.from_env(), we initialize the connection to our Redis database using the environment variables exported earlier.
  2. Increment Counter: Each time the root route (/) is accessed, Redis increments the counter key. This key-value pair is automatically created in Redis if it does not exist, and its value is incremented on each request.
  3. Display the Count: The number of visits is returned in the response as plain text.