Python – Sort by a particular digit count in elements

When it is required to sort by a particular digit count in elements, a method is defined that takes a list element as parameter and uses the count() and str() methods to determine the results.

Below is a demonstration of the same ?

Example

def sort_count_digits(element):
    return str(element).count(str(my_key))

my_list = [4522, 2452, 1233, 2465]

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

my_key = 2

print("The value of key is")
print(my_key)

my_list.sort(key=sort_count_digits)

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

Output

The list is :
[4522, 2452, 1233, 2465]
The value of key is
2
The result is :
[1233, 2465, 4522, 2452]

How It Works

The sorting function counts how many times the digit 2 appears in each number:

• 1233: Contains 0 occurrences of digit 2

• 2465: Contains 1 occurrence of digit 2

• 4522: Contains 2 occurrences of digit 2

• 2452: Contains 2 occurrences of digit 2

The list is sorted in ascending order based on these counts.

Alternative Approach Using Lambda

numbers = [4522, 2452, 1233, 2465]
target_digit = 2

# Using lambda function for cleaner code
sorted_numbers = sorted(numbers, key=lambda x: str(x).count(str(target_digit)))

print("Original list:", numbers)
print("Sorted by digit count:", sorted_numbers)

Original list: [4522, 2452, 1233, 2465]
Sorted by digit count: [1233, 2465, 4522, 2452]

Sorting by Multiple Digits

def count_specific_digits(number, digits):
    """Count occurrences of multiple digits in a number"""
    num_str = str(number)
    total_count = 0
    for digit in digits:
        total_count += num_str.count(str(digit))
    return total_count

numbers = [1234, 2255, 3456, 2222]
target_digits = [2, 5]

sorted_numbers = sorted(numbers, key=lambda x: count_specific_digits(x, target_digits))

print("Numbers:", numbers)
print("Sorted by count of digits 2 and 5:", sorted_numbers)

Numbers: [1234, 2255, 3456, 2222]
Sorted by count of digits 2 and 5: [1234, 3456, 2255, 2222]

Conclusion

Use the count() method on string representation of numbers to sort by digit frequency. Lambda functions provide a cleaner syntax for simple sorting operations.