sorting tuples in python

Question

I am trying to get the sorted output from following program.

"""Count words."""
    # TODO: Count the number of occurences of each word in s

    # TODO: Sort the occurences in descending order (alphabetically in case of ties)

    # TODO: Return the top n words as a list of tuples 


from operator import itemgetter
def count_words(s, n):
    """Return the n most frequently occuring words in s."""

    t1=[]
    t2=[]
    temp={}
    top_n={}

    words=s.split()
    for word in words:
        if word not in temp:
            t1.append(word)
            temp[word]=1
        else:
            temp[word]+=1
    top_n=sorted(temp.items(), key=itemgetter(1,0),reverse=True)

    print top_n

    return 


def test_run():
    """Test count_words() with some inputs."""
    count_words("cat bat mat cat bat cat", 3)
    count_words("betty bought a bit of butter but the butter was bitter", 3)


if __name__ == '__main__':
    test_run()

This program output is like:

[('cat', 3), ('bat', 2), ('mat', 1)]

[('butter', 2), ('was', 1), ('the', 1), ('of', 1), ('but', 1), ('bought', 1), ('bitter', 1), ('bit', 1), ('betty', 1), ('a', 1)]

but I need in the form like:

[('cat', 3), ('bat', 2), ('mat', 1)]

[('butter', 2), ('a', 1),('betty', 1),('bit', 1),('bitter', 1) ... rest of them here]

COuld you please let me know the best possible way?

They are immutable, but sort-able. And dict wouldn't fit here, unless you only use the array part of dictionary. Or if you change the question altogether. Lists would be an option, though. — Božo Stojković
– Božo Stojković, Commented Jul 17, 2016 at 19:16
can u guys suggest any modification in the above code only so that it gives the desired output — Manish Kumar
– Manish Kumar, Commented Jul 17, 2016 at 19:18

Blckknght · Accepted Answer · 2016-07-17 19:30:38Z

3

You need to change the key function you're giving to sorted, since the items in your desired output need to be sorted in descending order by count but ascending order alphabetically. I'd use a lambda function:

top_n = sorted(temp.items(), key=lambda item: (-item[1], item[0]))

By negating the count, an ascending sort gets you the desired order.

answered Jul 17, 2016 at 19:30

Blckknght

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2 Comments

Manish Kumar Over a year ago

can we limit the number of items to be return by sorted by passing any argument ?

Blckknght Over a year ago

No, sorted always sorts the whole list. To get just the first n values, use a slice: top_n = top_n[:n]

Ohad Eytan · Accepted Answer · 2016-07-17 19:30:30Z

0

You can change:

top_n=sorted(temp.items(), key=itemgetter(1,0),reverse=True)

To:

temp2=sorted(temp.items(), key=itemgetter(0),reverse=False)
top_n=sorted(temp2.items(), key=itemgetter(1),reverse=True)

and thanks to the Sort Stability you will be good

answered Jul 17, 2016 at 19:30

Ohad Eytan

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2 Comments

Manish Kumar Over a year ago

how temp2 shud be defined here? like this temp2={} ??

Ohad Eytan Over a year ago

@ManishKumar the first line define temp2, and the seconed use it. you don't need to initialize it.

Aran-Fey · Accepted Answer · 2016-07-17 19:31:02Z

0

Instead of itemgetter, use lambda t:(-t[1],t[0]) and drop the reverse=True:

top_n=sorted(temp.items(), key=lambda t:(-t[1],t[0]))

This returns the same thing as itemgetter(1,0) only with the first value inverted so that higher numbers will be sorted before lower numbers.

answered Jul 17, 2016 at 19:31

Aran-Fey

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Comments

Abhi V · Accepted Answer · 2016-07-17 19:34:23Z

def count_words(s, n):
"""Return the n most frequently occuring words in s."""

    t1=[]
    t2=[]
    temp={}
    top_n={}

    words=s.split()
    for word in words:
        if word not in temp:
            t1.append(word)
            temp[word]=1
        else:
            temp[word]+=1
    top_n=sorted(temp.items(), key=lambda t: (t[1], t[0]),reverse=True)

    print top_n

    return 


def test_run():
"""Test count_words() with some inputs."""
    count_words("cat bat mat cat bat cat", 3)
    count_words("betty bought a bit of butter but the butter was bitter", 3)


if __name__ == '__main__':
    test_run()

I used lambda instead of itemgetter and in other apps I've written, lambda seems to work.

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