set axis square?

Sorry if this is a silly question; i couldn't find the answer in the source files or the mailing list archive.

I am using matplotlib 0-60.2. Is there an equivalent in matplotlib to the matlab command 'axis square', to set the aspect ratio to 1? More generally, can i set the aspect ratio to any ratio i like? I am interested in this for plot() and scatter().

Thanks !
Dominique