How to count the occurrences of single items in a list of lists in descending order?

Question

x=[['apple', 'banana', 'carrot'],
['apple', 'banana'],
['banana', 'carrot']]

I want the result to look like this:

dict  = {'banana': 3,'apple': 2, 'carrot': 2}

Asked By: eliza nyambu

||

Source

Answer 1

You can "flatten" your x, and then just count, while iterating over unique elements of the (flat) x:

x = [['apple', 'banana', 'carrot'],
    ['apple', 'banana'],
    ['banana', 'carrot']]

flat_x = [a for b in x for a in b]
res = {a: sum(b == a for b in flat_x) for a in set(flat_x)}
print(res)
# {'carrot': 2, 'apple': 2, 'banana': 3}

Another way to flatten-out the list-of-lists is to use chain from itertools, so you can use:

from itertools import chain
flat_x = list(chain(*x))

Answered By: ShlomiF

Answer 2

One-liner solution (if you don’t mind the import):

import collections

lists = [
    ['apple', 'banana', 'carrot'],
    ['apple', 'banana'],
    ['banana', 'carrot']    
]

print(collections.Counter(
    item for sublist in lists for item in sublist).most_common())

Documentation: Counter.most_common, generator expressions.

Answered By: user3840170

How to count the occurrences of single items in a list of lists in descending order?

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