Updating query parameters in a link

[adam820]

Howdy! Is there a built-in way to build an href to a new URL that maintains the existing query params while updating one or more of them? Or would I need to build that myself out of the existing request object?

For example, I have a URL http://localhost:8000/?foo=bar&foo2=baz. I want to create a button/link with an HREF that points at the same URL, but with buz as the foo2 param: http://localhost:8000/?foo=bar&foo2=buz. This can be done manually (or with a helper function), but I wanted to make sure I wasn't overlooking a built-in function (a la Flask's url_for).

Thanks!

[elimintz]

@adam820 Is this what you are looking to do:

import justpy as jp

def link_test(request):
    wp = jp.WebPage()
    foo = request.query_params.get('foo', 'No foo' )
    foo2 = request.query_params.get('foo2', 'No foo2' )
    jp.Div(text=f'foo: {foo}, foo2: {foo2}', classes="m-4 text-xl", a=wp)
    jp.A(text='New link', href='http://localhost:8000/?foo=bar&foo2=buz', a=wp,
         classes='m-4 p-2 text-xl text-white bg-blue-500 hover:bg-blue-700')
    return wp

jp.justpy(link_test)

If not, please let me know

[adam820]

Sort of, but not quite. I figured it could be done manually, but I was checking to see if there was something that would auto-build the href with the query parameters already intact (by passing them in), to avoid having to manually hardcode addresses, etc.

I ended up making my own quick and dirty params builder function that updates an existing parameter, or otherwise accepts new parameters passed in as kwargs.

from urllib.parse import urlencode

def build_url_params(req_obj, **kwargs):
    # Copy the original query parameters over to a new mutable dict
    qparams = dict()
    for k, v in req_obj.query_params.items():
        qparams[k] = v
    try:
        # Build the query params
        for k, v in kwargs.items():
            if k in qparams.keys():
                qparams[k] = v
            else:
                qparams[k] = v
    except (ValueError, KeyError):
        return "?"

    return f"?{urlencode(qparams)}"

[matthoendorf]

I've created click functions for buttons that use wp.redirect

def button_click(self, msg):
    wp = msg.page
    wp.redirect = f'/page?param1={self.param1}&param2={self.param2}'

Not sure if this helps...

[adam820]

Not quite, since it looks like you're hardcoding parameters in the redirect. The part of url_for (from Flask) that I was inquiring about is thus: Variable arguments that are unknown to the target endpoint are appended to the generated URL as query arguments. You can pass in an arbitrary number of keyword arguments and the URL is auto-built with whatever is already there plus the new parameters.

Either way, I have moved on from this using this project at this time in my application; thanks for including that information for future readers!