How to set a value for an empy list

I am starting to learn to program using BeautifulSoup. What I want to achieve with this code is to save prices from different pages. To achieve this I store the prices of each page in a list and all those lists in a list. The problem is some pages do not save the prices so there are some lists that are completely empty. What I am looking for is that those empty lists are assigned the elements of the “ListaR” so that later I do not have problems. Here’s my code:

from bs4 import BeautifulSoup
import requests
import pandas as pd
from decimal import Decimal
from typing import List

AppID = ['495570', '540190', '607210', '575780', '338840', '585830', '637330', '514360', '575760', '530540', '361890', '543170', '346500', '555930', '575700', '595780', '362400', '562360', '745670', '763360', '689360', '363610', '575770', '467310', '380560'] 
ListaPrecios = list()
ListaUrl = list() #<------- LISTA
Blanco = [""]
ListaR = ["$0.00 USD", "$0.00 USD"]

for x in AppID: # <--------- Para cada una de las AppID...
    #STR# 
    url = "https://steamcommunity.com/market/search?category_753_Game%5B%5D=tag_app_"+x+"&category_753_cardborder%5B%5D=tag_cardborder_0&category_753_item_class%5B%5D=tag_item_class_2#p1_price_asc" # <------ Usa AppID para entrar a sus links de mercado
    ListaUrl += [url] # <---------- AGREGA CADA LINK A UNA LISTA

PageCromos = [requests.get(x) for x in ListaUrl]
SoupCromos = [BeautifulSoup(x.content, "html.parser") for x in PageCromos]
PrecioCromos = [x.find_all("span", {"data-price": True}) for x in SoupCromos] # <--------- GUARDA LISTAS DENTRO DE LISTAS CON CODIGO

min_CromoList = []

for item in PrecioCromos:
    CromoList = [float(i.text.strip('USD$')) for i in item]
    min_CromoList.append(min(CromoList)) # <---------------- Lista con todos los precios minimos de cromos de cada juego

print(min_CromoList)

Output: ValueError: min() arg is an empty sequence

Answer

You can change this line

min_CromoList.append(min(CromoList))

to:

if not CromoList:  # this will evaluate to True if the list is empty
    min_CromoList.append(min(ListaR))
else:
    min_CromoList.append(min(CromoList))

A neat feature of python is that empty lists evaluate to False and non-empty lists evaluate to True.

Since min(ListaR) will always evaluate to '$0.00 USD' it is probably neater to write this as:

if not CromoList:
    min_CromoList.append('$0.00 USD')
else:
    min_CromoList.append(min(CromoList))