Finding the average of a list

I have to find the average of a list in Python. This is my code so far

l = [15, 18, 2, 36, 12, 78, 5, 6, 9]
print reduce(lambda x, y: x + y, l)

I've got it so it adds together the values in the list, but I don't know how to make it divide into them?

On Python 3.4+ you can use statistics.mean()

l = [15, 18, 2, 36, 12, 78, 5, 6, 9]

import statistics
statistics.mean(l)  # 20.11111111111111

On older versions of Python you can do

sum(l) / len(l)

On Python 2 you need to convert len to a float to get float division

sum(l) / float(len(l))

There is no need to use reduce. It is much slower and was removed in Python 3.

l = [15, 18, 2, 36, 12, 78, 5, 6, 9]
sum(l) / len(l)

You can use numpy.mean:

l = [15, 18, 2, 36, 12, 78, 5, 6, 9]

import numpy as np
print(np.mean(l))

A statistics module has been added to python 3.4. It has a function to calculate the average called mean. An example with the list you provided would be:

from statistics import mean
l = [15, 18, 2, 36, 12, 78, 5, 6, 9]
mean(l)