trying to create a getPrincipal function [closed]

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trying to create a function to get the principal amount for a loan using the for loop for the sum of present values

def presentValue(amount, num_months, interest): 
    return (amount)/(1 + interest)**num_months

def getPrincipal(amount, num_months, interest):
    return
    getPrincipal = 0
    for presentValue in range(1,240):
    getPrincipal = getPrincipal + presentValue

something must be wrong here but no errors occur

A = 100
interest = 0.01
num_months = 240
P = getPrincipal(A, num_months, interest)
print(P)

doing print(P) returns None

The first line of getPrincipal says "return None and ignore the rest" so that's what it does. — Kenny Ostrom
– Kenny Ostrom, Commented Oct 21 at 18:45
If you try to run the code as shown in your question, you will get an error - specifically, an IndentationError exception — jackal
– jackal, Commented Oct 22 at 5:55

colonel · Accepted Answer · 2025-10-21 18:06:28Z

3

Your getPrincipal function was not correct. Here I made changes,

Added return statement: The function now returns totalPrincipal
Fixed the loop logic: Now properly iterates through each month from 1 to num_months
Used the presentValue function: Each iteration calculates the present value for that specific month

def presentValue(amount, num_months, interest): 
    return (amount)/(1 + interest)**num_months


def getPrincipal(amount, num_months, interest):
    totalPrincipal = 0
    for month in range(1, num_months + 1):
        pv = presentValue(amount, month, interest)
        totalPrincipal = totalPrincipal + pv
    return totalPrincipal

A = 100
interest = 0.01
num_months = 240
P = getPrincipal(A, num_months, interest)
print(P)

answered Oct 21 at 18:06

colonel

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