I made a workaround so that I don't heve to log in all the time. :-)
swap.bat is:
ren other.lwp temp.lwp
ren pywikibot.lwp other.lwp
ren temp.lwp pywikibot.lwp
del temp.lwp

So I have to type swap and everything is fine. But I still don't know if I have to use both accounts in one script. In compat there was a sysopname in config, and it automatically switched to that if it was needed.