How to count the frequency of the elements in an unordered list?

Question

I need to find the frequency of elements in an unordered list

a = [1,1,1,1,2,2,2,2,3,3,4,5,5]

output->

b =         


        

Answer 1

num=[3,2,3,5,5,3,7,6,4,6,7,2]
print ('\nelements are:\t',num)
count_dict={}
for elements in num:
    count_dict[elements]=num.count(elements)
print ('\nfrequency:\t',count_dict)

Answer 2

Data. Let's say we have a list:

fruits = ['banana', 'banana', 'apple', 'banana']

Solution. Then we can find out how many of each fruit we have in the list by doing this:

import numpy as np    
(unique, counts) = np.unique(fruits, return_counts=True)
{x:y for x,y in zip(unique, counts)}

Output:

{'banana': 3, 'apple': 1}

Answer 3

def frequencyDistribution(data):
    return {i: data.count(i) for i in data}   

print frequencyDistribution([1,2,3,4])

...

 {1: 1, 2: 1, 3: 1, 4: 1}   # originalNumber: count

Answer 4

Here's another succint alternative using itertools.groupby which also works for unordered input:

from itertools import groupby

items = [5, 1, 1, 2, 2, 1, 1, 2, 2, 3, 4, 3, 5]

results = {value: len(list(freq)) for value, freq in groupby(sorted(items))}

results

{1: 4, 2: 4, 3: 2, 4: 1, 5: 2}

Answer 5

from collections import Counter
a=["E","D","C","G","B","A","B","F","D","D","C","A","G","A","C","B","F","C","B"]

counter=Counter(a)

kk=[list(counter.keys()),list(counter.values())]

pd.DataFrame(np.array(kk).T, columns=['Letter','Count'])

Answer 6

For your first question, iterate the list and use a dictionary to keep track of an elements existsence.

For your second question, just use the set operator.