"min() arg error is empty sequence" error while trying to draw a count / barplot

Question

Currently learning to develop dashboard application with Shiny for Python, I am facing issues while trying to plot a graph with filtered data.

I am using an initial dataset, I want to filter using patient name or date I collect from data range selector or select box. To perform the data selection, I tried to setup a reactive function that make the row selection using pandas library.

When I want to display the graph (count plot for example), I receive the following message

min() arg is an empty sequence

I don't see this error if I directly plot the graph with non filtered data.

So I guess there is something wrong during the filtering step:

from shiny.express import input, render, ui
from shiny import reactive
import plotly.express as px
import pandas as pd
import numpy as np
import seaborn as sns
from shinywidgets import reactive_read, render_widget  

df_patient = pd.read_excel(r"C:\Users\rdesb\OneDrive\Bureau\MyAPP\dashboard\db_patient.xlsx", 
                           index_col="Indice")

df_ABS = pd.read_excel(r"C:\Users\rdesb\OneDrive\Bureau\MyAPP\dashboard\Bdd_ABS.xlsx")
liste_patient = pd.unique(df_ABS["Patient"])
liste_patient = tuple(liste_patient)

#df_patient["Date de naissance"] = pd.to_datetime(df_patient["Date de naissance"], format='%d-%m-%Y')

#INTERFACE GRAPHIQUE

ui.page_opts(title="DashBoard Plume", fillable=True)

with ui.nav_panel("Informations Patients"):
    ui.h2("Informations Patients")
    @render.data_frame  
    def patients_df():
        return render.DataGrid(df_patient)  

        
with ui.nav_panel("Statistiques"):

    with ui.layout_columns():  

        with ui.card(full_screen=False, height=100):  
            ui.card_header("Selection de date")
            ui.input_date_range("daterange", "Date range", start="2020-01-01") 
            

        with ui.card(full_screen=False, height=100):  
            ui.card_header("Selection patient")
            
            ui.input_select(  
                "patient_select",  
                "Choisissez un patient:",  
                liste_patient,  )  
     
    @reactive.Calc                
    def df_ABS_sorted():
        return df_ABS.loc[df_ABS["Patient"]== {input.patient_select()}]

    with ui.layout_columns():
        with ui.card(full_screen=False, height=700):  
            @render.plot(alt="Affichage données triées par patient et date")  
            def plot():  
                ax = sns.countplot(data=df_ABS_sorted(), x="Patient")  
                ax.set_title("Absences")
                ax.set_xlabel("Nom")
                ax.set_ylabel("Counts")
                return ax  
            
            @render.text
            def value():
                return f"{input.patient_select()}"

I also tried not using reactive calculation and directly type the "filtered" conditions, that lead to the same error.

I guess there is something wrong typing directly

df_ABS.loc[df_ABS["Patient"]== {input.patient_select()}]

maybe something conflcit with the type?