NumPy Financial functions: nper() function

Last update on August 19 2022 21:50:38 (UTC/GMT +8 hours)

numpy.nper() function

The nper() function is used to compute the number of periodic payments.

decimal.Decimal type is not supported.

Syntax:

numpy.nper(rate, pmt, pv, fv=0, when='end')

Version: 1.15.0

Parameter:

Name	Description	Required / Optional
rate	Rate of interest (per period) array_like	Required
pmt	Payment array_like	Required
pv	Present value array_like	Required
fv	Future value array_like	Optional
when	When payments are due ('begin' (1) or 'end' (0)) {{'begin', 1}, {'end', 0}}, {string, int}	Optional

Notes:

The number of periods nper is computed by solving the equation:

fv + pv*(1+rate)**nper + pmt*(1+rate*when)/rate*((1+rate)**nper-1) = 0

but if rate = 0 then:

fv + pv + pmt*nper = 0

NumPy.nper() method Example-1:

If you only had $200/month to pay towards the loan, how long would it take to pay-off a loan of $10,000 at 8% annual interest?

>>> import numpy as np
>>> print(np.round(np.nper(0.08/12, -200, 10000), 2))

Output:

61.02

NumPy.nper() method Example-2:

So, over 64 months would be required to pay off the loan.

The same analysis could be done with several different interest rates and/or payments and/or total amounts to produce an entire table.

>>> import numpy as np
>>> np.nper(*(np.ogrid[0.07/12: 0.08/12: 0.01/12,
...                    -150   : -99     : 50    ,
...                    8000   : 9001    : 1000]))

Output:

array([[[ 64.07334877,  74.06368256],
        [108.07548412, 127.99022654]],

       [[ 66.12443902,  76.87897353],
        [114.70165583, 137.90124779]]])

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