Given a list of strings, return characters that appear in more than one string

Question

I'm trying to implement a function which receives a variable number of strings and returns characters that appear at least in two strings:

test_strings = ["hello", "world", "python", ]

print(test(*strings))

{'h', 'l', 'o'}

Answer 1

Remove duplicates from the strings (by making sets of the characters of each string), then create a Counter that counts the number of inputs strings that each character appeared in

from collections import Counter
from itertools import chain

def test(*strings, n=2):
    sets = (set(string) for string in strings)
    counter = Counter(chain.from_iterable(sets))
    return {char for char, count in counter.items() if count >= n}


print(test("hello", "world", "python"))  # {'o', 'h', 'l'}

Answer 2

A one-liner using sets and collections.Counter:

from collections import Counter

test_strings = ["hello", "world", "python"]

letters = {k for k, v in Counter([l for x in test_strings for l in set(x)]).items() if v > 1}

Output:

>>> letters
{'o', 'l', 'h'}

Answer 3

The following function find_duplicates should do the work

def find_duplicates(string_list):
    """
    Given a list of strings, return characters that appear in more than one string
    """
    # Create a dictionary to store the characters and their counts
    char_count = {}

    # Iterate over the string and add the characters to the dictionary
    for string in string_list:
        for char in string:
            if char in char_count:
                char_count[char] += 1
            else:
                char_count[char] = 1

    # Create a list to store the characters that appear at least twice
    duplicates = []
    # Iterate over the dictionary and add the characters to the list
    for char, count in char_count.items():
        if count > 1:
            duplicates.append(char)
    # Return the list of duplicates
    return duplicates

Now let's test using the list of strings you give as an example

test_strings = ["hello", "world", "python"]

print(find_duplicates(test_strings))

[Out]: ['h', 'l', 'o']