item frequency count in python

Question

I'm a python newbie, so maybe my question is very noob. Assume I have a list of words, and I want to find the number of times each word appears in that list. Obvious way to do this is:

words = "apple banana apple strawberry banana lemon"
uniques = set(words.split())
freqs = [(item, words.split.count(item)) for item in uniques]
print(freqs)

But I find this code not very good, because this way program runs through words list twice, once to build the set, and second time counting the number of appearances. Of course, I could write a function to run through list and do the counting, but that wouldn't be so pythonic. So, is there a more efficient and pythonic way?

Answer 1

I happened to work on some Spark exercise, here is my solution.

tokens = ['quick', 'brown', 'fox', 'jumps', 'lazy', 'dog']

print {n: float(tokens.count(n))/float(len(tokens)) for n in tokens}

**#output of the above **

{'brown': 0.16666666666666666, 'lazy': 0.16666666666666666, 'jumps': 0.16666666666666666, 'fox': 0.16666666666666666, 'dog': 0.16666666666666666, 'quick': 0.16666666666666666}

Answer 2

Use reduce() to convert the list to a single dict.

words = "apple banana apple strawberry banana lemon"
reduce( lambda d, c: d.update([(c, d.get(c,0)+1)]) or d, words.split(), {})

returns

{'strawberry': 1, 'lemon': 1, 'apple': 2, 'banana': 2}

Answer 3

Can't you just use count?

words = 'the quick brown fox jumps over the lazy gray dog'
words.count('z')
#output: 1

Answer 4

If you are using python 2.7+/3.1+, there is a Counter Class in the collections module which is purpose built to solve this type of problem:

>>> from collections import Counter
>>> words = "apple banana apple strawberry banana lemon"
>>> freqs = Counter(words.split())
>>> print(freqs)
Counter({'apple': 2, 'banana': 2, 'strawberry': 1, 'lemon': 1})
>>> 

Since both 2.7 and 3.1 are still in beta it's unlikely you're using it, so just keep in mind that a standard way of doing this kind of work will soon be readily available.

Answer 5

words = "apple banana apple strawberry banana lemon"
w=words.split()
e=list(set(w))       
for i in e:
   print(w.count(i))    #Prints frequency of every word in the list

Hope this helps!

Answer 6

Standard approach:

from collections import defaultdict

words = "apple banana apple strawberry banana lemon"
words = words.split()
result = collections.defaultdict(int)
for word in words:
    result[word] += 1

print result

Groupby oneliner:

from itertools import groupby

words = "apple banana apple strawberry banana lemon"
words = words.split()

result = dict((key, len(list(group))) for key, group in groupby(sorted(words)))
print result