Python program to extract Mono-digit elements

When it is required to extract mono-digit elements (numbers where all digits are the same), list comprehension and the all operator are used.

What are Mono-digit Elements?

Mono-digit elements are numbers where all digits are identical, such as 1, 22, 333, 4444, etc. For single-digit numbers, they are naturally mono-digit.

Example

my_list = [863, 1, 463, "pyt", 782, 241, "is", 639, 4, "fun", 22, 333]

print("The list is :")
print(my_list)

my_result = [item for item in my_list if isinstance(item, int) and all(str(digit) == str(item)[0] for digit in str(item))]

print("The result is :")
print(my_result)

Output

The list is :
[863, 1, 463, 'pyt', 782, 241, 'is', 639, 4, 'fun', 22, 333]
The result is :
[1, 4, 22, 333]

How It Works

The list comprehension performs the following steps:

• isinstance(item, int) ? Filters only integer values from the list

• str(item)[0] ? Gets the first digit of the number as a string

• all(str(digit) == str(item)[0] for digit in str(item)) ? Checks if all digits match the first digit

• Returns only numbers where all digits are identical

Alternative Approach Using Function

def extract_mono_digit_elements(data):
    mono_digits = []
    for item in data:
        if isinstance(item, int):
            str_item = str(item)
            if len(set(str_item)) == 1:  # All digits are same
                mono_digits.append(item)
    return mono_digits

my_list = [863, 1, 463, 782, 241, 639, 4, 22, 333, 5555]
result = extract_mono_digit_elements(my_list)

print("Original list:", my_list)
print("Mono-digit elements:", result)

Original list: [863, 1, 463, 782, 241, 639, 4, 22, 333, 5555]
Mono-digit elements: [1, 4, 22, 333, 5555]

Conclusion

Use list comprehension with all() to extract mono-digit elements efficiently. The isinstance() check ensures only integers are processed, while all() verifies all digits are identical.