如何使用MRJob从文本文件计算平均值

Question

I am a beginner with MrJob and having trouble calculating an average prime number from a text file of prime numbers. I am unsure at which part to apply arithmetic logic and also whether I should yield lists when using MrJob. The text file contains one million primes and this is what I've come up so far, I don't understand what the key value should be in my case.

%%writefile prime_average.py
from mrjob.job import MRJob

class primeAverages(MRJob):

def mapper(self, _, line):
    results = []
    for x in line.split():
        if(x.isdigit()):
            yield x, 1

def reducer(self, word, key):
    yield word, sum(word)/len(key)

Answer 1

you can use something like:

def mapper(self, _, line):
    if line.isdigit():
        yield (None, int(line))

def reducer(self, key, values):
    s = 0 #sum of primes
    c = 0 #number of primes
    for p in values:
        s += p
        c += 1
    yield (None, s / c)