Mod_python error: "PythonHandler webshop"

Traceback (most recent call last):

  File "C:\Python24\lib\site-packages\mod_python\apache.py", line 299, in HandlerDispatch
    result = object(req)

  File "C:/www/script/\webshop.py", line 59, in handler
    i.show()

  File "C:/www/script/\shop.py", line 59, in show
    self.shopping()

  File "C:/www/script/\shop.py", line 87, in shopping
    elif infobutton!="": self.artikelinfo()

  File "C:/www/script/\shop.py", line 389, in artikelinfo
    artikel=self.artikelDB.artikelsuche("","",artikelnr)[0]

IndexError: tuple index out of range