Calculate the difference between two venmo users

venmo.py

import csv
import sys

me = ''
them = ''
paid_to_me = 0
paid_to_them = 0
payment_from_them = 0
payment_to_them = 0

with open(sys.argv[1], 'r') as f:
    r = csv.reader(f)
    for line in r:
        is_payment = True if line[3] == 'Payment' else False
        is_charge = True if line[3] == 'Charge' else False
        frm = line[6]
        to = line[7]
        if not (is_payment or is_charge):
            continue
        amount = float(line[8][3:])

        if is_payment and frm == them and to == me:
            payment_from_them += 1
            paid_to_me += amount
        if is_payment and frm == me and to == them:
            payment_to_them += 1
            paid_to_them += amount
        if is_charge and frm == them and to == me:
            paid_to_them += amount
        if is_charge and frm == me and to == them:
            paid_to_me += amount
    print(f'''{me} paid {them}: {paid_to_them}. Number of times: {payment_to_them}
{them} paid {me}: {paid_to_me}. Number of times: {payment_from_them}
difference: {max(paid_to_them, paid_to_me) - min(paid_to_me, paid_to_them)}, total payments: {payment_from_them + payment_to_them}''')