The query string is the part of a request following the URL, preceded by a ? mark.

Example: https://encrypted.google.com/search?hl=en&q=stack%20overflow

For this example, we are making a simple echo webserver that echos back everything submitted to it via the echo field in GET requests.

Example: localhost:5000/echo?echo=echo+this+back+to+me

Flask Example:

from flask import Flask, request

app = Flask(import_name=__name__)

@app.route("/echo")
def echo():

    to_echo = request.args.get("echo", "")
    response = "{}".format(to_echo)

    return response

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

Flask also allows access to a CombinedMultiDict that gives access to both the request.form and request.args attributes under one variable.

This example pulls data from a form field name submitted along with the echo field in the query string.

Flask Example:

from flask import Flask, request

app = Flask(import_name=__name__)


@app.route("/echo", methods=["POST"])
def echo():

    name = request.values.get("name", "")
    to_echo = request.values.get("echo", "")

    response = "Hey there {}! You said {}".format(name, to_echo)

    return response

app.run()

You can access the form data submitted via a POST or PUT request in Flask via the request.form attribute.

from flask import Flask, request

app = Flask(import_name=__name__)


@app.route("/echo", methods=["POST"])
def echo():

    name = request.form.get("name", "")
    age = request.form.get("age", "")

    response = "Hey there {}! You said you are {} years old.".format(name, age)

    return response

app.run()