Compsci 101, Fall 2015, October 29-1

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Names

netid

These questions based on function countup from Counter.py

def countup(words):
pairs = [(w,words.count(w)) for w in words]
return sorted(set(pairs))

Which one of the following is true?

The value returned is a list of tuples, it has as many tuples as there are strings in parameter words

The value returned is a list of lists, it has as many lists as there are strings in parameter words

The value returned is a list of tuples, it has as many tuples as there are unique strings in parameter words

The value returned is a list of lists, it has as many lists as there are unique strings in parameter words

Clear selection

In the code above, how many times is words.count called if the parameter words contains 100 strings?

100

1,000

10,000

100,000

Clear selection

The function call words.count(w) must examine every string in words to see if it's equal to w in returning a count. If words contains 100 strings, how many times is words[0] checked to see if it's equal to a string w across all the calls of words.count(w)

100

1,000

10,000

100,000

Clear selection

If instead of creating a set in the return statement, the list comprehension is changed to using a set as shown below, which of the following are true about the code (more than one statement may be true)?

pairs = [(w,words.count(w)) for w in set(words)]

For most files the revised code will be much faster because the function call words.count(w) happens far fewer times with the change

the revised code will not work correctly if words contains no repeat, e.g., it's a list of 1,000 unique words each occurring once

there is a list of words so that the revised code would be roughly a million times faster than the original code

there is a list of words such that the revised code would be roughly a million times slower than the original code

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