Multiselectbox with lists as options

Using Streamlit
1

Hello there,

i’m sorry if the following is a trivial task but i’ve been trying to wrap my head around it and just couldn’t find a solution by myself.

I want to create a multiselectbox where a user can choose between multiple lists instead of strings.

A quick example what i’m trying to achieve:

list_1 = ['1','2','3','4']
list_2 =  ['a','b','c','d']
list_3 =  ['!','?','€','%']

choice = st.multiselect('Choose List',[list_1,list_2,list_3])
 
df = df[df['symbol'].isin(choice )]

While the example above sort of works it will logically display the list inside the selectbox.
But i would like to select a string so “choice” is equal to the selected list.
I would also need to join the lists if multiple options are selected.

I need a little hint here what would be the best way to do this.
Thanks in advance for anyone taking his/her time for me.

2

It is unclear what you want. Do you want the options to be displayed as strings in the widget? That is already happening. Do you want multiselect to return a string? That cannot happen, it always return a list. Do you want to return a list of strings? Then the options must be strings.

There is no selected list. This is a multiselect so there will be a list of selected options. Since the options themselves are lists, that will be a list of selected lists.

That’s easy: sum(choice, []).

3

Sorry if i didn’t describe it clearly enough.

I want the widget to display the string name (list_1, list_2 and list_3)
and when one options is selected it returns the selected list.

In my example above the widget would display the options like

['1','2','3','4']
['a','b','c','d']
['!','?','€','%']

Since i didn’t input string values but my lists.
Which then would return a list within a list i guess but that’s not what i want.

So for example if i select “list_1”
choice = ['1','2','3','4']
And if i would select “list_1” and “list_3”
choice = ['1','2','3','4','!','?','€','%']

4

So you want the widget to display this in he dropdown?

list_1
list_2
list_3

Looks easy enough:

names = st.multiselect("Choose List", options=["list_1", "list_2", "list_3"])

As I already said, there is no way a multiselect can do that. You can write code, though. There is life beyond the widgets.

For that you need a mapping between the names and the lists. That is what python dictionaries are for:

lists_by_name = {
    "list_1": ["1", "2", "3", "4"],
    "list_2": ["a", "b", "c", "d"],
    "list_3": ["!", "?", "€", "%"],
}

Now you can convert the list of selected names in a list of selected lists:

lists = [lists_by_name[name] for name in names]

And finally merge the selected lists as I explained in my previous post:

choice = sum(lists, [])
5

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