interest_calc.py

interest_calc.py

from typing import Union


def separate_number(number: str, sep: str = ""):
    result = number[::-1]
    insert_idx = []
    times = 0
    for idx in range(len(number)):
        if idx % 3 == 0:
            insert_idx.append(idx + times)
            times += 1

    for i in insert_idx:
        result = result[:i] + sep + result[i:]

    return result[::-1][:-1]  # Return reversed result, with final separator removed


def print_number(number: Union[float, int] = 0, sep: str = ""):
    if len(sep) > 1:
        print("INVALID SEPARATOR")
    result = str(number)

    if sep:
        parts = result.split(".")
        result = separate_number(parts[0], sep)
        result += "." + parts[1]

    return result


print("--           CPD INTEREST CALCULATOR          --")
print("________________________________________________")
print("Principal                                       ", end="")
principal = float(input())
print("Interest Rate (p.a. %)                          ", end="")
ir = float(input()) / 100
print("Period (years)                                  ", end="")
pd = float(input())
print("Subdivision                                     ")
print("(M)onthly, (Y)early, (H)alf-yearly, (Q)uarterly ", end="")
dv_s = input().lower()

if dv_s == "m":
    dv = 12
elif dv_s == "y":
    dv = 1
elif dv_s == "h":
    dv = 2
elif dv_s == "q":
    dv = 4
else:
    dv = 0
    exit(1)

ir_orig = ir
pd_orig = pd

ir /= dv
pd *= dv

amount = principal * (1 + ir) ** pd
interest = amount - principal

print()
print(f"PERIODS                   = {pd_orig} * {dv}")
print(f"                          = {int(pd)}")
print(f"INTEREST RATE PER PERIOD  = {ir_orig * 100:.3f}% / {dv}")
print(f"                          = {ir * 100:.3f}%")
print()
print(
    f"AMOUNT                    = ${print_number(principal, sep=',')} * (1 + {ir * 100:.3f}%) ^ {int(pd)}"
)
print(f"                          = ${amount:.3f}...")
print(f"                          = ${amount:.0f} (cor. to nearest dollar)")
print()
print(f"INTEREST                  = ${amount} - ${print_number(principal, sep=',')}")
print(f"                          = ${interest:.3f}...")
print(f"                          = ${interest:.0f} (cor. to nearest dollar)")