4.6. Cookies in Flask

Flask provides built-in methods to set, read, and delete cookies using the request and response objects.

4.6.1. Setting a Cookie

from flask import Flask, render_template, make_response

app = Flask(__name__)


@app.route("/")
def index():
    response = make_response(render_template("index.html"))
    response.set_cookie("user_id", "12345")
    return response


app.run(debug=True, reloader_type="stat", port=5000)

Explanation

• make_response(render_template("index.html")) creates a Response object with the rendered template in the body.

• response.set_cookie("user_id", "12345") stores a cookie with the name user_id and value 12345.

4.6.2. Setting Cookie Attributes

from flask import Flask, render_template, make_response

app = Flask(__name__)


@app.route("/")
def index():
    response = make_response(render_template("index.html"))
    response.set_cookie(
        "user_id", "12345", httponly=True, secure=True, samesite="Strict"
    )
    return response


app.run(debug=True, reloader_type="stat", port=5000)

Explanation

Parameter name and value pairs after the cookie name and value are treated as cookie attributes. In this example they are:

• httponly=True

• secure=True

• samesite="Strict"

The parameter name of cookie attribute names are:

• all lowercase

• have dashes - replaced with underscores _

For example Max-Age becomes max_age.

4.6.3. Reading a Cookie

from flask import Flask, request, make_response


@app.route("/get_cookie")
def get_cookie():
    user_id = request.cookies.get("user_id")  # Retrieve cookie
    if user_id:
        return f"User ID from cookie: {user_id}"
    return "No cookie found"


@app.route("/")
def index():
    response = make_response(render_template("index.html"))
    response.set_cookie(
        "user_id", "12345", httponly=True, secure=True, samesite="Strict"
    )
    return response

Explanation

Cookie values can be accessed through the request object which is available in flask routes.

• request.cookies.get("user_id") fetches the stored cookie value

4.6.4. Deleting a Cookie in Flask

from flask import Flask, request, make_response


@app.route("/delete_cookie")
def delete_cookie():
    response = make_response("Cookie deleted!")
    response.set_cookie("user_id", "", max_age=0)  # Set expiration to 0 to delete
    return response


@app.route("/")
def index():
    response = make_response(render_template("index.html"))
    response.set_cookie(
        "user_id", "12345", httponly=True, secure=True, samesite="Strict"
    )
    return response


app.run(debug=True, reloader_type="stat", port=5000)

Explanation

To remove a cookie, set its Max-Age to 0 past using set_cookie(max_age=0). This instructs the browser to immediately expire the cookie.

Code Challenge: Cookie Jar 🍪

Create a flask app with a single page that shows the current value for a cookie and allows the user to set the value.

Note

When you close the app and re-open the app your cookie value should still be there!

You have been provided with a scaffold that contains a starting flask app and template.

Do not modify the index.html template.

Note

Once you’ve completed the requirements you can test your site by opening the page, setting a cookie value and closing the page. If you re-open the page your cookie data should still show on the page. You can also view the cookie data in your browser’s developer tools.

Instructions

You should only edit the index_post() function

1. Get the new cookie value from the form data

new_value = request.form.get("cookie_value", None)

2. If new_value is not None:

2.1. Make a response object from the rendered template

response = make_response(render_template("index.html", cookie_value=new_value))

2.2. Set the cookie value in the response with a 1 day expiration

response.set_cookie("cookie_data", new_value, max_age=86400)

2.3 Return the response object

return response

3. Otherwise redirect to “/”`

Download the scaffold and write your code in app.py.

SCAFFOLD_cookie_jar.zip

Solution

Solution is locked