Selenium-Python : Variable name . send keys throws error

s.find_element_by_xpath("//*[@id='container']/div/div[1]/div[1]/div[2]/div[2]/form/div/div/input").send_keys("car")

The above code works fine

but

cars=s.find_element_by_xpath("//*[@id='container']/div/div[1]/div[1]/div[2]/div[2]/form/div/div/input")
cars.send_keys("car")

This one throws error raise exception_class(message, screen, stacktrace) selenium.common.exceptions.StaleElementReferenceException: Message: stale element reference: element is not attached to the page document

So variable assignment and calling functions with variables is not a good way?