Summary
Copies the specified parameter by index to another parameter in the script tool. The specified parameters must be of the same data type.
Syntax
CopyParameter (from_param, to_param)
| Parameter | Explanation | Data Type | 
from_param  | The index position of the parameter to be copied.  | Integer | 
to_param  | The index position of the parameter that will be copied to.  | Integer | 
Code sample
Copy input parameter to output parameter.
import arcpy
# Copy the script tool's specified input parameter object
#  to the script tool's specified output parameter.
arcpy.CopyParameter(0, 1)