topic Re: multiply values from fieldlist into new field in Python Questions

multiply values from fieldlist into new field

ErikMartin — Wed, 18 Jan 2012 13:04:00 GMT

Hi,

I am trying to select a subset of fields and multiply the values into a new field. I am having no problems creating a list of fields. From there I'm not sure if I should be using CalculateField_managment or an UpdateCursor. Or both? Any help or direction would be greatly appreciated. Although I;ve tried several avenues, I haven't gotten very far yet...

import arcpy arcpy.env.workspace = r"K:\Data\PythonTest.gdb" fc = "FeatureClass"  #Create list of fields that begin with "WR_" .. I want to multiply all of these together and write values to a new field "Product" FieldList = arcpy.ListFields(fc, "WR_*", "All") rows = arcpy.UpdateCursor(fc)  for field in FieldList:     fName = field.name     print fName  #Everything up to here works-- I get a list of the fields I want      #Open an update cursor for row in rows:     for field in FieldList:         CurrVal = row.getValue(field)  # this doesn't work & I'm not sure how to proceed from here

Re: multiply values from fieldlist into new field

MathewCoyle — Wed, 18 Jan 2012 13:18:53 GMT

I think you are just missing some minor things. Take this as an example.

rows = arcpy.UpdateCursor(fc) for row in rows:     Val = 1     for field in fieldList:         CurrVal = row.getValue(field.name)         Val = Val * CurrVal # Or whatever you want to do to the values     row.NewField = Val     rows.updateRow(row)

Re: multiply values from fieldlist into new field

ErikMartin — Wed, 18 Jan 2012 13:45:16 GMT

Thanks, Matthew. That was exactly what I needed. Here's my final code, in case anyone else is interested.

import arcpy
arcpy.env.workspace = r"K:\Data\PythonTest.gdb"
fc = "FeatureClass"

#create update Cursor
rows = arcpy.UpdateCursor(fc)

#Create list of fields that begin with "WR_" .. I want to multiply all of these together and write values to a new field "Product"
FieldList = arcpy.ListFields(fc, "WR_*", "All")
for field in FieldList:
    fName = field.name
    print fName
for row in rows:
    Val = 1
    for field in FieldList:
        CurrVal = row.getValue(field.name)
        print CurrVal
        Val = Val * CurrVal
        row.setValue("Product", Val) #updates values to "product" field
        rows.updateRow(row)