Consider the following reducer code: 1 #!/usr/bin/env python3
2 # length_reducer.py
3 """Counts the number of words with each length."""
4 import sys
5 from itertools import groupby
6 from operator import itemgetter
7
8 def tokenize_input():
9 """Split each line of standard input into a key and a value."""
10 for line in sys.stdin:
11 yield line.strip().split(' ')
12
13 # produce key-value pairs of word lengths and counts separated by tabs
14 for word_length, group in groupby(tokenize_input(), itemgetter(0)):
15 try:
16 total = sum(int(count) for word_length, count in group)
17 print(word_length + ' ' + str(total))
18 except ValueError:
19 pass # ignore word if its count was not an integer
Which of the following statements a), b) or c) is false?
A) Function tokenize_input is a generator function that reads and splits the key-value pairs produced by the mapper.
B) The mapper script sends its output directly to the reducer script.
C) For each line, tokenize_input strips any leading or trailing whitespace (such as the terminating newline) and yields a list containing the key and a value.
D) All of the above statements are true.

Question

Consider the following reducer code: 1 #!/usr/bin/env python3
2 # length_reducer.py
3 """Counts the number of words with each length."""
4 import sys
5 from itertools import groupby
6 from operator import itemgetter
7
8 def tokenize_input():
9 """Split each line of standard input into a key and a value."""
10 for line in sys.stdin:
11 yield line.strip().split('	')
12
13 # produce key-value pairs of word lengths and counts separated by tabs
14 for word_length, group in groupby(tokenize_input(), itemgetter(0)):
15 try:
16 total = sum(int(count) for word_length, count in group)
17 print(word_length + '	' + str(total))
18 except ValueError:
19 pass # ignore word if its count was not an integer
Which of the following statements a), b) or c) is false?
A) Function tokenize_input is a generator function that reads and splits the key-value pairs produced by the mapper.
B) The mapper script sends its output directly to the reducer script.
C) For each line, tokenize_input strips any leading or trailing whitespace (such as the terminating newline) and yields a list containing the key and a value.
D) All of the above statements are true.

Quizplus · Accepted Answer

A and C are true statements. A describes the tokenize_input function accurately as a generator function that processes input lines into key-value pairs. C correctly states that tokenize_input handles each line by stripping whitespace and yielding a list of the key and value. However, B is false because the mapper script does not send its output directly to the reducer script in a Hadoop or MapReduce environment. Instead, the Hadoop framework handles the shuffling and sorting of mapper outputs before they are passed to the reducer.

Consider the Following Reducer Code: 1 #!/Usr/bin/env Python3