error 000861: Destination field is not valid:

Discussion created by altair1981 on Apr 10, 2014
Latest reply on Apr 11, 2014 by altair1981
Hi everyone,

First I would like to highlight that  I´m an absolut newby with python.
I trying to use this already created python tool but keep on receiving this error message: error 000861: Destination field is not valid:

It's a nested code so would be difficult to put all the different variables but the specific part of the code that is giving this problem is this:

gp.CostPath_sa("samp_lyr", cd_name, bl_name, "cost_path", "BEST_SINGLE", "")

All the input variables are fine, the only error cames from the last one (destination field) wich it´s supposed to be an optional variable. That´s why the "", because is empty. 

Any suggestions??

Hope can understand the post.