ln (Natural Log) in Python

In this assignment I have completed all the problems except this one. I have to create a python script to solve an equation (screenshot).

Unfortunately, in my research all over the internet I cannot figure out how in the world to either convert ln to log or anything usable, or anything. The code I have written so far is below. I will also post the answer that our teacher says we should get.

import math p = 100 r = 0.06 / 12 FV = 4000 n = str(ln * ((1 + (FV * r) / p) / (ln * (1 + r)))) print ("Number of periods = " + str(n)) 

The answer I should get is 36.55539635919235 Any advice or help you have would be greatly appreciated!

Also, we are not using numpy. I already attempted that one.

Thanks!

2 Answers

math.log is the natural logarithm:

From the documentation:

math.log(x[, base]) With one argument, return the natural logarithm of x (to base e).

Your equation is therefore:

n = math.log((1 + (FV * r) / p) / math.log(1 + r))) 

Note that in your code you convert n to a str twice which is unnecessary

Here is the correct implementation using numpy (np.log() is the natural logarithm)

import numpy as np p = 100 r = 0.06 / 12 FV = 4000 n = np.log(1 + FV * r/ p) / np.log(1 + r) print ("Number of periods = " + str(n)) 

Output:

Number of periods = 36.55539635919235