#!/usr/bin/env python
from selenium import webdriver
def singleton(cls):
    instances = {}
    def getinstance():
        if cls not in instances:
            instances[cls] = cls()
        return instances[cls]
    return getinstance
@singleton
class Firefox(webdriver.Firefox):
    pass
if __name__ == '__main__':
    Firefox().get('https://www.ya.ru')
    Firefox().get('https://www.google.com')

 from selenium import webdriver
class Chrome(webdriver.Chrome):
    def __new__(cls, *args, **kwargs):
        if not hasattr(cls, '_instance'):
            cls._instance = super().__new__(cls, *args, **kwargs)
            super().__init__(cls._instance, *args, **kwargs)
        return cls._instance
    def __init__(self, *args, **kwargs):
        pass