import requests
from bs4 import BeautifulSoup

url = 'https://www.geny.com/reunions-courses-pmu?date=2021-08-20'

headers = {
    'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:70.0) Gecko/20100101 Firefox/70.0',
    'Accept': 'text/html,*/*',
    'Accept-Language': 'en,en-US;q=0.7,en;q=0.3',
    'X-Requested-With': 'XMLHttpRequest',
    'Connection': 'keep-alive'}

resp = requests.get(url, headers=headers)
soup = BeautifulSoup(resp.text, 'lxml')

# using find
a = soup.find('div', {'class': 'yui-u liensReunion'})
print(a.get('href'))