emi.py

def calculate_monthly_installment(
    principal, 
    rate_of_intrest, 
    duration, 
    processing_fee_percent=0):
    """
    This method should calculate monthly installment

    params:
      prinicpal: Amount of the product purchased
      rate_of_intrest: rate of interest (10.5 => 0.105)
      duration: duration in months
      processing_fee_percent: processing fee percent default is zero

    Returns:
       monthly installment
    """
    rate_of_intrest_pm= rate_of_intrest/12
    emi = principal * rate_of_intrest_pm * ((1 + rate_of_intrest_pm)**duration)/((1 + rate_of_intrest_pm)**duration-1)
    return emi


if __name__ == '__main__':
    print(calculate_monthly_installment(
        principal=100000,
        rate_of_intrest=0.065,
        duration=60))