How to query a stock with the Yahoo Finance API by ISIN?

You can query Yahoo finance to get the Yahoo ticker symbol using elemental (which is basically selenium). Here is the code:

import json
import elemental
import yfinance
import urllib.parse as urlparse
from urllib.parse import parse_qs

def get_quote(symbol):
    msft = yfinance.Ticker(symbol)
    try:
        hist = msft.history(period="2d")
    except json.decoder.JSONDecodeError:
        return None
    try:
        hist.reset_index(inplace=True)
        jsdata = json.loads(hist.to_json())
        return jsdata["Close"]["0"]
    except (ValueError, KeyError) as e:
       return None


def web_lookup(browser, isin):
    # Search PyPI for Elemental.
    browser = elemental.Browser()
    browser.visit("https://finance.yahoo.com/lookup")
    browser.get_input(id="yfin-usr-qry").fill(isin)
    browser.get_button(type="submit").click()

    time.sleep(5)

    parsed = urlparse.urlparse(browser.url)
    try:
        ticker = parse_qs(parsed.query)['p'][0]
    except KeyError:
        ticker = "n/a"
    browser.quit()
    return ticker

When you call the function web_lookup essentially the lookup page will, be opened, the ISIN will be entered into the search box, and the browser eventually navigates to the Yahoo page with the Yahoo ticker symbol, which will be extracted from the URL the browser navigates to. The code then tries to use this ticker symbol to get the quotes from the last two days using the yahoo finance API. If that all works fine, the function returns a working Yahoo ticker symbol, or n/a in case something did not work.