Accessing query parameters in Flask

Introduction

Query parameters let you send extra information in a web address. Accessing them helps your app respond differently based on what the user asks.

When you want to filter a list of items on a webpage, like showing only red shirts.

When you want to remember user choices, like sorting order or page number.

When you want to pass small bits of data without changing the page content.

When building search features that take input from the URL.

When you want to share links that include specific settings or filters.

Syntax

Flask

from flask import request

value = request.args.get('parameter_name')

request.args holds all query parameters as a dictionary-like object.

Use .get() to safely get a parameter value or None if missing.

Examples

Gets the value of the 'color' query parameter.

Flask

color = request.args.get('color')

Gets 'page' parameter or defaults to '1' if not provided.

Flask

page = request.args.get('page', '1')

Converts all query parameters into a regular Python dictionary.

Flask

all_params = request.args.to_dict()

Sample Program

This Flask app has a route '/search' that reads query parameters 'q' and 'page'. It shows them in the response. If 'page' is missing, it uses '1' as default.

Flask

from flask import Flask, request

app = Flask(__name__)

@app.route('/search')
def search():
    query = request.args.get('q', '')
    page = request.args.get('page', '1')
    return f"Search query: {query}, Page: {page}"

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

Important Notes

Query parameters are always strings. Convert them if you need numbers.

If a parameter appears multiple times, request.args.get() returns the first one.

Use request.args.getlist('param') to get all values if repeated.

Summary

Query parameters add extra info to URLs for flexible web responses.

Use request.args.get() to read them safely in Flask.

Always handle missing parameters by providing defaults or checks.