"dracula571" wrote: >> dracula571 wrote: >> >> > but k[-6:2] = [1,2] >> > why k[-6:2] is [1,2]not [].i do follow (3),to make i positive by >> > plusing len(k) twice. >> >> twice? > > that is -6 + len(k) + len(k) =4 sure, but what makes you think you should add the length twice? </F>