Average of all values in a list - is there a more 'Pythonic' way to do this?

Question

So I'm following a beginner's guide to Python and I got this exercise:

Create a list containing 100 random integers between 0 and 1000 (use iteration, append, and the random module). Write a function called average that will take the list as a parameter and return the average.

I solved it easily in a few minutes but the chapter also mentions several ways to traverse through lists and assign multiple values to lists and variables that I'm not sure if I fully understand yet, so I don't know if it's possible to do this in less lines. This is my answer:

import random

def createRandList():
    newlist = []
    for i in range(100):
        newint = random.randrange(0,1001)
        newlist.append(newint)
    return newlist

def average(aList):
    totalitems = 0
    totalvalue = 0
    for item in aList:
        intitem = int(item)
        totalitems = totalitems + 1
        totalvalue = totalvalue + intitem
    averagevalue = totalvalue/totalitems
    return averagevalue

myList = createRandList()
listAverage = average(myList)

print(myList)
print(listAverage)

Thanks in advance!

score 9 · Accepted Answer · edited Nov 29 '16 at 20:06

9

Using Python's builtin sum and len functions:

print(sum(myList)/len(myList))

edited Nov 29 '16 at 20:06

John Y

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answered Jan 30 '14 at 01:27

jayelm

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And createRandList could be expressed as ```[random.randrange(0, 1001) for i in range(100)]``` – nathancahill Jan 30 '14 at 01:29
Thanks a lot! Glad to find out `sum` works on lists. – reggaelizard Jan 30 '14 at 01:29
3

Also, Python variables are typically lower_case_with_underscores instead of mixedCase. my_list instead of myList. – nathancahill Jan 30 '14 at 01:33
That's good to know, I've just been following the convention used in the guide but I'll definitely do this in the future. – reggaelizard Jan 30 '14 at 01:34

score 1 · Answer 2 · answered Jan 30 '14 at 01:46

1

I agree with the suggestion above about using sum.

Though I don't love using a list comprehension just to run a fixed number of iterations, your createRandList function body could be simply:

return [random.randint(0,1000) for i in range(100)]

(Also, I find randint a little more readable because the "stop" value is the one you want, not the one you want + 1. )

In any case, you can dispense with the line where you call int() on your numbers -- the output of randrange is already int.

answered Jan 30 '14 at 01:46

Paul Bissex

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Although `randint` appeals to a more universal common sense, `randrange` is preferred due to its consistency with Python convention, e.g. `range(start, stop)` and the slice syntax (`[start, stop]`). In fact, randint has been deprecated multiple times in python history. See http://stackoverflow.com/a/2568917/2980246 – jayelm May 27 '14 at 04:22

Average of all values in a list - is there a more 'Pythonic' way to do this?

2 Answers2