# ln (Natural Log) in Python

## Question:

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!

## Answers:

`math.log`

is the natural logarithm:

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
```