Is there any pythonic way to find average of specific tuple elements in array?

Question

I want to write this code as pythonic. My real array much bigger than this example.

( 5+10+20+3+2 ) / 5

print(np.mean(array,key=lambda x:x[1])

Answer 1

With pure Python:

from operator import itemgetter

acc = 0
count = 0

for value in map(itemgetter(1), array):
    acc += value
    count += 1

mean = acc / count

An iterative approach can be preferable if your data cannot fit in memory as a list (since you said it was big). If it can, prefer a declarative approach:

data = [sub[1] for sub in array]
mean = sum(data) / len(data)

If you are open to using numpy, I find this cleaner:

a = np.array(array)

mean = a[:, 1].astype(int).mean()

Answer 2

You can simply use:

print(sum(tup[1] for tup in array) / len(array))

Or for Python 2:

print(sum(tup[1] for tup in array) / float(len(array)))

Or little bit more concisely for Python 2:

from math import fsum

print(fsum(tup[1] for tup in array) / len(array))