The way I know of sending keys using the WebDriver Python bindings is as follows:
How can I send a key (specifically the Escape key) to no element in particular, just to the window in general?
WebDriver offers the ability to cope with multiple windows. This is done by using the "WebDriver.switchTo().window()" method to switch to a window with a known name. If the name is not known, you can use "WebDriver.getWindowHandles()" to obtain a list of known windows. You may pass the handle to "switchTo().window()".