CODEWITHSUNDEEP
pythonlistdictionary
Pinkzy
Pinkzy

Reputation: 9

Creating histogram from list

This question was a part of the the interview process and I couldn't figure it out.

Given a list of integers, create a histogram where the output is a dictionary. The key are the elements in the list and the values are the count of elements in the list.

For example, inputlist: [2,3,4,2,5,7,3,2,4] and expected output: {2:3,3:2,4:2..}

I know there has to be a loop iterating over the list and then inserting those values in the dictionary. But I messed up on the syntax bad. Would appreciate if somebody could guide me with syntax or pseudocode. HELP!

Upvotes: 0

Views: 940

Answers (3)

LockeErasmus
LockeErasmus

Reputation: 116

This would be my solution using dictionary comprehension:

inputlist = [2,3,4,2,5,7,3,2,4]
result = {k:inputlist.count(k) for k in set(inputlist)}

However I agree that Counter from collections would probably perform better as the inputlist would get bigger (see list.count() vs Counter() performance)

Upvotes: 2

Akas Antony
Akas Antony

Reputation: 749

Try this:

from collections import Counter

inputlist = [2,3,4,2,5,7,3,2,4]
freq_counter = Counter(inputlist)

print(freq_counter)

Upvotes: 1

ᴓᴓᴓ
ᴓᴓᴓ

Reputation: 1166

For future reference you can't just provide the question, you need to provide a minimum reproducible example.

Here's the answer anyways:

output = {}
inputlist = [2,3,4,2,5,7,3,2,4] 
for num in inputlist:
  if num in output:
    output[num] += 1
  else:
    output[num] = 1
print(output)

Upvotes: 1

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