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Asked: 2024-09-25T14:56:12+05:30 In:

Frequency First: How to Deduplicate and Sort a List based on Item Frequency in Python?

I’ve been diving into some Python programming lately, and I stumbled upon a really interesting problem that I thought I’d share and get your thoughts on. So, here’s the scenario: imagine you have a list of items, and the goal is to remove any duplicates, but there’s more to it! Not only do we want to eliminate the repeats, but we also want to order the items based on how many times they appeared in the original list. The more frequent they are, the higher they should be ranked.

Let’s say I have this list: `[“apple”, “banana”, “banana”, “cherry”, “apple”, “date”, “apple”, “banana”, “fig”]`. The first step is, of course, to get rid of the duplicates. So, we go from that mess to just unique fruits: `[“apple”, “banana”, “cherry”, “date”, “fig”]`. Easy enough, right?

But then comes the part that really gets my brain working. We need to sort those unique fruits by the count of how many times they appeared in the original list. So, in this case, “apple” appeared 3 times, “banana” 3 times, “cherry” 1 time, “date” 1 time, and “fig” 1 time. That would mean “apple” and “banana” should be at the top of our new list, but they both have the same count. This raises the question: how do you handle ties?

One approach could be to maintain alphabetical order for items with the same frequency, which would give us the final result as `[“apple”, “banana”, “cherry”, “date”, “fig”]`.

I tried playing around with lists and dictionaries, but I keep running into challenges when it comes to sorting. I’m curious to hear how you would tackle this! Whether you use built-in functions or create a cool custom sorting mechanism, I’d love to see your solutions. What tips and tricks do you have for efficiently solving this problem? Can you do it in the least amount of code possible, or perhaps you’ve got an interesting approach that’s not about the code length but more about the elegance? Looking forward to your responses!

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    2 Answers






    1. Python Sorting Challenge

      Sorting Fruits by Frequency

      Okay, here’s a way to tackle the problem you shared! It seems pretty fun! 😊 Let’s break it down step by step.

      Step 1: Count the Occurrences

      First, we need to count how many times each fruit appears in the original list. We can use a dictionary to help with that!

      
# Original list of fruits
fruits = ["apple", "banana", "banana", "cherry", "apple", "date", "apple", "banana", "fig"]

# Dictionary to count occurrences
count_dict = {}
for fruit in fruits:
    count_dict[fruit] = count_dict.get(fruit, 0) + 1

      Step 2: Create a Sorted List

      Next, we make a list of unique fruits and sort them based on their counts, and if there’s a tie, we’ll sort them alphabetically!

      
# Sort based on frequency and then alphabetically
sorted_fruits = sorted(count_dict.keys(), key=lambda x: (-count_dict[x], x))

      Final Output

      Now, if we print sorted_fruits, we should get the sorted list!

      
print(sorted_fruits)  # Output: ['apple', 'banana', 'cherry', 'date', 'fig']

      So, the final sorted list is [“apple”, “banana”, “cherry”, “date”, “fig”]! 🎉

      That’s how I’d do it. Hope this helps you out!


    2. To tackle this problem in Python, we can use the `collections.Counter` to count the frequency of each item and sort the unique items based on their frequencies. In case of ties, sorting them alphabetically will ensure a consistent order. Here’s a concise implementation:

      from collections import Counter

def sort_items(items):
    # Count the frequency of items
    frequency = Counter(items)
    # Sort items first by frequency (in descending order), then alphabetically
    sorted_items = sorted(frequency.keys(), key=lambda x: (-frequency[x], x))
    return sorted_items

# Example usage
items_list = ["apple", "banana", "banana", "cherry", "apple", "date", "apple", "banana", "fig"]
result = sort_items(items_list)
print(result)

      This program effectively counts the occurrences of each fruit and sorts them based on their frequency while maintaining alphabetical order for those that appear the same number of times. When you run the code with the provided `items_list`, the output will be `[‘apple’, ‘banana’, ‘cherry’, ‘date’, ‘fig’]`, fulfilling the requirements of the problem succinctly.

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