If these are the classes offered by http://genevaswing.ch/ then I am fairly certain that you don't need a partner join.  

I started Lindy Hop a little over a year ago, and at least half the class had signed up individually, so don't hesitate - it's great fun!  I will look forward to meeting you at the social dances after your class every Tuesday evening at Les Halles.

I just checked the website, and can confirm that:

"Les leaders s’inscrivant seuls seront pris d’emblée."