Class that implements a complete MapReduce in Python.

mapreduce.py

from itertools import groupby
from functools import reduce as functools_reduce
from operator import itemgetter

class MapReduce(object):
    """
    Class that emulates the behaviour of an actual map-reduce
    infrastructure. 
    """
    def map(self, pairs: dict, map_function):
        return map(map_function, pairs.keys(), pairs.values())
    
    def shuffle(self, mapper):
        for newpair in groupby(
                sorted(mapper,
                       key=itemgetter(0)),
                key=itemgetter(0)):
            yield newpair            

    def reduce(self, pairs, reduce_function):
        for pair in pairs:
            yield pair[0], functools_reduce(
                reduce_function, pair[1], [])

    def run(self, pairs, map_function, reduce_function):
        for result in self.reduce(self.shuffle(
                self.map(pairs, map_function)),
                                reduce_function):
            yield result