module webbrowser - open link in same window - osx

[robin]

hi,

i'm using the webbrowser module to open url's in safari or firefox.
specifically i'm using the
webbrowser.open('http://...', new=0)
command.

however, even though i say new=0 my url is always opened in a new
browser window.
what can i do, so my link is opened in an already open browser window?

thank you for your help,

robin