[FIXED] Flask render_template() does not send context parameters in requests

Issue

I am working on an app, and I want to send some parameters to render a page properly.

Here is my Flask code:

@app.get('/main')
def interface():
    if True:  # here supposed to be a function to check authorization
        s = 'HELLO'  # for testing purposes I hardcode the dummy parameter
        return render_template('main.html', sid=s)
    return redirect('/')  # if not authorized, move home

When I run the app and try to open 127.0.0.1:5000/main , the parameter is not passed. I can see it in the developer console:

However if I write the address manually, like 127.0.0.1:5000/main?sid=HELLO, I see this:

What am I doing wrong?

Solution

The render_template('main.html', sid=s) means Flask will respond to the the /main path with the contents from the main.html template, and to generate that template the sid=HELLO will be used.

If you want Flask to redirect to a different path with a GET variable in the path, you would have to use url_for, example:

return redirect(url_for("user.logout", user="admin")

See these two routes that may explain:

@main_blueprint.route("/login")
def login():
    # lets assume your login processing determines the credentials submitted are for admin:
    user = "admin"
    return redirect(url_for("main_blueprint.user", id=user))

@main_blueprint.route("/user/<id>")
def user(id):
    return "welcome user: {}".format(id)

by doing a GET to /login, you will be redirected to /user/admin.

Answered By - ilias-sp