# Fast Python file entropy

I was looking for a fast and simple algorithm to calculate entropy of some bytes in Python. I found Ero Carreras post which contains a simple Python implementation. Using the *collections* module I could speed it up 4.5 times :) !

I tested it against *scipy.stats.entropy* and other variations but this was the fastest variation I found:

```
def entropy(data):
e = 0
counter = collections.Counter(data)
l = len(data)
for count in counter.values():
# count is always > 0
p_x = count / l
e += - p_x * math.log2(p_x)
return e
```