Sorry if this has been asked and answered. I did a search but came up empty.
There's actually a fairly easy way to do this. There's a method called 'set_window_position' which accepts negative values. So I wanted the browser to open on my left screen, so a simple negative 1000px pixels dragged it in enough for the maximize_window to pick the left screen.
driver.set_window_position(-1000, 0)
driver.maximize_window()
So depending on the screen sizes and where you want it to go, make some calculations and just drag it there!
Source: http://selenium-python.readthedocs.io/api.html#module-selenium.webdriver.firefox.webdriver (picked firefox for this example)