Using Search/Update Cursor?

Question

I am trying to get field values from one table and use them to perform calculations on a row in another fc table. Does anyone have any ideas on how to make this run faster? I've tried a dictionary but am having problems when i try to reassign a value in the dictionary.

import arcpy
import numpy as np


arcpy.env.workspace = "C:\Users\michellep\Documents\project.gdb"

print "Arcpy & Numpy imported successfully and workspace set"
print "Start Processing"
start = time.time()
#define variables
group = "Test_Group"
fields = ['ObjectID', 'R', 'A', 'Total']
pc = "PC_Table"

cursor = arcpy.da.UpdateCursor(group, fields)
    #row = cursor.next()
for row in cursor:
    R = row[0]
    A = row[1]
    arcpy.CalculateField_management(pc, "R", R, "PYTHON", "")
    arcpy.CalculateField_management(pc, "A", A, "PYTHON", "")
    arcpy.CalculateField_management(pc, "WVal", "!R! / !A! * (!B! / !A!)**(!R!-1), "PYTHON", "")
    arcpy.CalculateField_management(pc, "Hours", "!WVal! * !K!", "PYTHON", "")
    arr = arcpy.da.TableToNumPyArray(pc, "Hours")
    arr.dtype = np.dtype(float)
    row[2] = np.sum(arr)
    cursor.updateRow(row)
    del row

del cursor
end = time.time()
processTime = end - start
print "Processing Completed - {:.1f} seconds".format(processTime)

Answer 1

It looks like you're trying to update each row using calculate field. Calculate field performs the calculation on the entire table. Something like this is probably what you're looking for:

arcpy.env.workspace = "C:\Users\michellep\Documents\project.gdb"

print "Arcpy & Numpy imported successfully and workspace set"
print "Start Processing"
start = time.time()
#define variables
group = "Test_Group"
fields = ['ObjectID', 'R', 'A', 'Total']
pc = "PC_Table"

cursor = arcpy.da.UpdateCursor (group, fields)
for oid, r, a, total in cursor:
    total = (r * a) / (B / a) ** (r * -1)
    row = (oid, r, a, total)
    cursor.updateRow(row)

Note: variable B is not defined in the script.