Scraping data from a table in python
The markup is definitely not easy to parse because of the nested table elements with no meaningful attributes. But, you are right that relying on relative index of a table and the desired cell being the 6th in the table is quite a fragile strategy.

Instead, let's use the row title as our "anchor". Then, we'll get the following cell via the .find_next_sibling():

DESIRED_MONEDAS = "DOLAR USA"

label = soup.find(lambda tag: tag.name == "td" and tag.get_text(strip=True) == DESIRED_MONEDAS)
value = label.find_next_sibling("td").get_text(strip=True)
print(value)