Просто запустить программу?
import subprocess
subprocess.run(["firefox"])
Выполнить какое-то действие через браузер на сайте и получить результат?
Смотри в Selenium - это могучий инструмент. Типа
from selenium import webdriver
from selenium.common.exceptions import TimeoutException
from selenium.webdriver.support.ui import WebDriverWait # available since 2.4.0
import time
# Create a new instance of the Firefox driver
driver = webdriver.Firefox()
# go to the google home page
driver.get("http://www.google.com")
# find the element that's name attribute is q (the google search box)
inputElement = driver.find_element_by_name("q")
# type in the search
inputElement.send_keys("Cheese!")
# submit the form (although google automatically searches now without submitting)
inputElement.submit()
# the page is ajaxy so the title is originally this:
print driver.title
try:
# we have to wait for the page to refresh, the last thing that seems to be updated is the title
WebDriverWait(driver, 10).until(lambda driver : driver.title.lower().startswith("cheese!"))
# You should see "cheese! - Google Search"
print driver.title
finally:
driver.quit()
https://docs.seleniumhq.org
https://www.selenium2.ru 
