Python CSV demonstration

calculation.py

import csv
import math

def diameter(rad):
    return rad*2


def surface(rad):
    return 4*math.pi*pow(rad,2)


def volume(rad):
    return (4/3)*(math.pi*pow(rad,3))


with open('spheres.csv', 'r+') as input_csv:
    # Read the CSV.
    csv_reader = csv.reader(input_csv, delimiter=',')
    # Set a tracker for if we're reading
    # the header row.
    header = True
    # Empty list of rows that we'll store
    # use to store our calculations.
    output_csv = []
    for row in csv_reader:
        # Are we at the header row?
        if header:
            # Add new headers.
            header = False
            output_csv.append(row + ["diameter","surface","volume"])
            # Go to the next line of the file.
            continue
        # Find and assign the radius.
        radius = float(row[2])
        # Append our calculations to the end of each row.
        output_csv.append(row + [diameter(radius),surface(radius),volume(radius)])
    # Set position to the beginning of the file.
    input_csv.seek(0)
    # Write our new, calculated data to the original CSV.
    csv.writer(input_csv, delimiter=',').writerows(output_csv)

spheres-after-processing.csv

spheres.csv