[Zope] append() and spaces

Hallo, I've got a strange problem. I use RESPONSE.redirect and pass values the usual way --> ('car?bought=1&amount=%s')%(Amount) where Amount is a list-variable. I build Amount dynamically with the append-method, and strangely I can't pass this variable(Error: Bad Request) because Python puts spaces between the values ->[1, 3, 4] So, I have to extract the list and build a new string but this is very uncomfortable! Any hint? Thanks!