This seems like a nice, concise book on probability and statistics for Python programmers: Think Stats.

# Standard Deviation in Python

I just wanted to go through the process of calculating standard deviation today, and this is how I did it in Python. Python makes such a nice calculator :)

```
>>> s = [2,4,4,4,5,5,7,9]
>>> def average(s): return sum(s) * 1.0 / len(s)
...
>>> avg = average(s)
>>> avg
5.0
>>> variance = map(lambda x: (x - avg)**2, s)
>>> variance
[9.0, 1.0, 1.0, 1.0, 0.0, 0.0, 4.0, 16.0]
>>> average(variance)
4.0
>>> import math
>>> standard_deviation = math.sqrt(average(variance))
>>> standard_deviation
2.0
>>>
```