Add Paystack fees in Python

PaystackFee.py

import math

class PaystackFee:
    """Work with Paystack's Fees"""
    DEFAULT_PERCENTAGE = 0.015
    DEFAULT_ADDITIONAL_CHARGE = 10000
    DEFAULT_THRESHOLD = 250000
    DEFAULT_CAP = 200000

    percentage = DEFAULT_PERCENTAGE
    additional_charge = DEFAULT_ADDITIONAL_CHARGE
    threshold = DEFAULT_THRESHOLD
    cap = DEFAULT_CAP

    chargeDivider = 0
    crossover = 0
    flatlinePlusCharge = 0
    flatline = 0

    def __init__(self):
        self.__setup()

    def withPercentage(self, percentage):
        self.percentage = percentage
        self.__setup()

    def withAdditionalCharge(self, additional_charge):
        self.additional_charge = additional_charge
        self.__setup()

    def withThreshold(self, threshold):
        self.threshold = threshold
        self.__setup()

    def withCap(self, cap):
        self.cap = cap
        self.__setup()

    def __setup(self):
        self.chargeDivider = self.__chargeDivider()
        self.crossover = self.__crossover()
        self.flatlinePlusCharge = self.__flatlinePlusCharge()
        self.flatline = self.__flatline()

    def __chargeDivider(self):
        return 1 - self.percentage

    def __crossover(self):
        return (self.threshold * self.chargeDivider) - self.additional_charge

    def __flatlinePlusCharge(self):
        return (self.cap - self.additional_charge) / self.percentage

    def __flatline(self):
        return self.flatlinePlusCharge - self.cap

    def addFor(self, amountinkobo):
        if (amountinkobo > self.flatline):
            return int(round(amountinkobo + self.cap))
        elif (amountinkobo > self.crossover):
            return int(round((amountinkobo + self.additional_charge) / self.chargeDivider))
        else:
            return int(round(amountinkobo / self.chargeDivider))

Usage.py

from PaystackFee import PaystackFee

r = PaystackFee()
print r.addFor(530000)

# to add foreign payment costs...
r.withAdditionalCharge(10000)
r.withThreshold(250000)
r.withCap(10000000000000)
r.withPercentage(0.039)

print r.addFor(530000)