Passing a variable to redirect url_for in flask

Question

I was wondering if it is possible to pass a value through redirect(url_for()) with out it becoming a GET.

Basic example: I have a home function:

@app.route("/")
def home(msg=None):
    return render_template("home.html", mgs=msg)

how can I pass an message to the home function? In other words can I do this:

@app.route("/logout")
def logout():
    logout_user()
    return render_template('home.html', msg="logged out")

with redirect(url_for())?

this:

@app.route("/logout")
def logout():
    logout_user()
    return redirect(url_for('home', msg="logged out"))

just gives me the url with a get /?msg='logged out'.

I understand that url_for is generating an url based on the name of the function being passed to it. Can you pass a value to that function?

A gross (but not totally impractical) way would be to use a session variable, but other than that, No you cannot. — CodeLikeBeaker
– CodeLikeBeaker, Commented Aug 2, 2017 at 19:20
You can, if the URL is expecting that variable. So if your route was "/logout/:message", that would work, but then your URL would end up as "/logout/logged out" which would be even more horrible. (Although note there's nothing at all gross about using sessions; that's exactly what they're for.) — Daniel Roseman
– Daniel Roseman, Commented Aug 2, 2017 at 19:23

cowbert · Accepted Answer · 2017-08-02 20:45:50Z

5

What about a flash variable?

flash("logged out")
return redirect(url_for('home'))

Then in template for home:

{% with passed = get_flash_messages() %}
{% if passed %}
    <!-- passed should contain 'logged out' -->
{% endif %}

see also: http://flask.pocoo.org/docs/0.12/patterns/flashing/

answered Aug 2, 2017 at 20:45

cowbert

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Comments

sscalvo · Accepted Answer · 2020-07-21 14:13:56Z

3

Another way to go is using sessions:

Dont forget to add it to your imports

from flask import Flask, ..., session

In logout definition store the message in the session:

@app.route("/logout")
def logout():
    logout_user()
    session['msg'] = "logged out"
    return redirect(url_for('home'))

In the home function

@app.route("/")
def home(msg=None):
    return render_template("home.html", msg=session['msg'])

In the home template just use it as a usual variable:

<p>Dear user, you have been {{ msg }} </p>

This way you avoid using get and Flask takes care of all

answered Jul 21, 2020 at 14:13

sscalvo

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Comments

Mohamed Emad · Accepted Answer · 2017-08-02 19:17:41Z

0

No, I Do not think so, but you can use GET parameters like:

redirect('home?msg=You%20are%20loged%20in')

and instead of using a template to do the work you can use JS

answered Aug 2, 2017 at 19:17

Mohamed Emad

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3 Comments

lciamp Over a year ago

Yeah, I wanted to use the value passed in the template. Seems messy using the GETs. (user can make page say what ever) I guess I'll just used render_template when needed.

Mohamed Emad Over a year ago

I am not following here, What is wrong with the user changing the text that the page says?

lciamp Over a year ago

nothing wrong, I was just trying to avoid using GETs

Roger Hayashi · Accepted Answer · 2021-02-25 16:01:58Z

0

Did you try this?

msg="logged out"
return redirect(url_for('home'),code=307)

Code 307 is used as "POST"

edited Feb 25, 2021 at 16:01

answered Feb 21, 2021 at 1:47

Roger Hayashi

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Comments

Davi A. Sampaio · Accepted Answer · 2023-05-12 06:34:21Z

0

Just use an f-string in your route direction.

redirect(f'/route/{variable}')

edited May 12, 2023 at 6:34

Davi A. Sampaio

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answered Mar 16, 2023 at 20:23

Benjamin Coleman Gragson ES

1

1 Comment

Lover of Structure Over a year ago

There seems to be a missing closing parenthesis ) in your answer.

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