Map Reduce Paradigm. How to run two .py files in the same Command Prompt line

I am coding Map Reduce paradigm and it is working fine in command prompt as .py

    #map reduce paradigm
    #mapper

    data=["This is delhi\n", "This is paris\n", "This is Moscow\n"]

    #create a new file and leave it open to write over it
    file = open("jose.txt","w+")

    for line in data:
        #remove leading and trailing whitespace - choosing every line
        line=line.strip()
        #split the line into words
        words=line.split()
        #increase counters
        for word in words:
            file.write("%s\t%s" % (word,1))
            file.write("\n")
            print("%s\t%s" % (word,1))
            file.close()

    #Map reduce paradigm
    #reducer

    from operator import itemgetter import sys

    current_word = None current_count = 0 word = None

    file = open("jose.txt","r") lines = file.readlines() lines.sort()

    # input comes from STDIN for line in lines:
    # remove leading and trailing whitespace
    line = line.strip()

    # parse the input we got from mapper.py
    word, count = line.split()

    # convert count (currently a string) to int
    count = int(count)

    if current_word == word:
        current_count += count
    else:
        if current_word:
            # write result to STDOUT
            print ('%s\t%s' % (current_word, current_count))
        current_count = count
        current_word = word

    # do not forget to output the last word if needed!
    if current_word == word:
        print ('%s\t%s' % (current_word, current_count))

    file.close()

The output is

This 1
is 1
delhi 1
This 1
is 1
paris 1
This 1
is 1
Moscow 1

Moscow 1
This 3
delhi 1
is 3
paris 1

It is good, but my professor is asking now:

1. Generate .py and execute it from command prompt, typing only "python mapper.py". It is easy, I did it.

2. Generate two .py files, one mapper the other one reducer, and execute them typing only "python reducer.py mapper.py" I cannot do it.

In some way the output of mapper.py have to be the input of reducer.py. Basically is the same code than in step 1, but I have to split it and then link the output of mapper.py with the input of reducer.py