# ln (Natural Log) in Python

## ln (Natural Log) in Python

`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
```