# Passing URL querystring to callback
**URL:** https://community.plotly.com/t/passing-url-querystring-to-callback/79570
**Category:** Dash Python
**Tags:** question
**Created:** [October 24, 2023, 8:32am UTC](https://community.plotly.com/t/passing-url-querystring-to-callback/79570 "2023-10-24T08:32:52Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@davzup89](https://community.plotly.com/u/davzup89)
#### Post date: [October 24, 2023, 8:32am UTC](https://community.plotly.com/t/passing-url-querystring-to-callback/79570/1 "2023-10-24T08:32:52Z")
In my dash app I can pass the \*\*kwargs to layout components like dropdown in a following manner:
```auto
def dropdown1(**kwargs):
return dbc.Col(
dcc.Dropdown(
id='dropdown1',
options=options_dropdown(),
value=kwargs.get("value1"),
) )
```
All the following dropdowns in my app are dependent on chosen value in the first dropdown. The callback(s) for those dropdowns would always override their respective kwargs in the layout.
I tried to pass \*\*kwargs to callback like:
```auto
@callback(
Output("dropdown2", "options"),
Output("dropdown2", "value"),
Input("dropdown1", "value"),
prevent_initial_call=False
)
def update_dropdown2 (dropdown1_value, **kwargs):
if not dropdown1_value:
return [], []
dropdown2_kwarg = kwargs.get('value2')
if dropdown2_kwarg is not None:
dropdown2_kwarg = dropdown2_kwarg [0]
dropdown2_opts = get_dropdown2_opts(dropdown1_value)
all_values = [option['value'] for option in dropdown2_opts]
if dropdown2_kwarg is not None:
return All_strenght_opts, [dropdown2_kwarg]
return dropdown2_opts, all_values
```
This does not work either. Also, with Input(‘\_pages\_location’, ‘path’), I get
> Property “path” was used with component ID: “\_pages\_location” in one of the Input items of a callback. This ID is assigned to a dash\_core\_components.Location component in the layout, which does not support this property.
Also tried
```auto
@callback(
Output("dropdown2", "options"),
Output("dropdown2", "value"),
Input("dropdown1", "value"),
Input('_pages_location', 'pathname'),
prevent_initial_call=True
)
def update_dropdown2 (dropdown1_value, path):
parsed_url = urlparse(path)
query_params = parse_qs(parsed_url.query)
Dropdown2_kwarg = query_params.get('phase')
```
but the returned kwarg is None eventhough it’s present in URL
---
### Author:  [@jinnyzor](https://community.plotly.com/u/jinnyzor)
#### Post date: [October 24, 2023, 10:05am UTC](https://community.plotly.com/t/passing-url-querystring-to-callback/79570/2 "2023-10-24T10:05:51Z")
Hello @davzup89,
I believe that you are looking for `search` from the `_pages_location`.
[https://dash.plotly.com/dash-core-components/location](https://dash.plotly.com/dash-core-components/location)
You’ll need to parse it out into the keywords because it just gives you the raw string.
Something like mentioned here could work:
> **[urllib.parse — Parse URLs into components](https://docs.python.org/3/library/urllib.parse.html)**
>
> Source code: Lib/urllib/parse.py This module defines a standard interface to break Uniform Resource Locator (URL) strings up in components (addressing scheme, network location, path etc.), to combi...
---
### Author:  [@davzup89](https://community.plotly.com/u/davzup89)
#### Post date: [October 24, 2023, 10:35am UTC](https://community.plotly.com/t/passing-url-querystring-to-callback/79570/3 "2023-10-24T10:35:25Z")
> [@davzup89](#):
>
> ```auto
> url = urlparse(path)
>
> query_params = parse_qs(parsed_url.query)
>
> ```
Thanks!
‘search’ was it.
I am already parsing this way:
```
parsed_url = urlparse(path)
query_params = parse_qs(parsed_url.query)
```
---
### Author:  [@davzup89](https://community.plotly.com/u/davzup89)
#### Post date: [October 24, 2023, 11:05am UTC](https://community.plotly.com/t/passing-url-querystring-to-callback/79570/4 "2023-10-24T11:05:00Z")
I found out as long as the URL is present in the browser, the dropdown values would now revert to those in URL instead of previously defined callback behavior.
This is quite problematic because I would only want to filter dropdowns with URL when the URL is first sent (when enter is press in the browser input field). I though using Input instead of State with \_pages\_location would do that but apparently not.
Is this kind of behavior achievable with Dash?
I guess, the search would need to revert back to None/null after being used for that.
```auto
parsed_url = urlparse(path)
query_params = parse_qs(parsed_url.query)
value_kwarg = query_params.get('value')
if value_kwarg :
value_kwarg = value_kwarg[0].split(',')
All_sets = options_dropdown(inputs)
if value_kwarg:
return All_sets, value_kwarg
return All_sets, [All_sets[-1]["value"]] if All_sets else []
```
---
### Author:  [@jinnyzor](https://community.plotly.com/u/jinnyzor)
#### Post date: [October 24, 2023, 11:20am UTC](https://community.plotly.com/t/passing-url-querystring-to-callback/79570/5 "2023-10-24T11:20:14Z")
You should be using ctx.triggered to figure out what is changing.
Also, if you are changing the pathname directly when crafting, you will always be triggering it.
What you can do is merge the callbacks and use the ctx.triggered to keep the callbacks from becoming circular.
Another thing you can do, is to make sure the built query string doesn’t equal the current query string, if so, do no update.
---
### Author:  [@davzup89](https://community.plotly.com/u/davzup89)
#### Post date: [October 24, 2023, 1:25pm UTC](https://community.plotly.com/t/passing-url-querystring-to-callback/79570/6 "2023-10-24T13:25:44Z")
Hmm, does changing url indeed trigger the callback via Input(‘\_pages\_location’, ‘search’)?
Because with my code I get empty dropdown if trying to pass kwargs from URL. Snippets below:
```auto
if not ctx.triggered:
return [], []
triggered_id, triggered_prop = ctx.triggered[0]["prop_id"].split(".")
if triggered_id == '_pages_location' and value_kwarg:
return All_opts, value_kwarg
elif triggered_id == 'dropdown1':
return All_opts, all_values
```
---
### Author:  [@jinnyzor](https://community.plotly.com/u/jinnyzor)
#### Post date: [October 24, 2023, 3:00pm UTC](https://community.plotly.com/t/passing-url-querystring-to-callback/79570/7 "2023-10-24T15:00:05Z")
I believe that changing the string triggers the layout being loaded again.
Place a print in the layout to verify. 🙂