Python – Extract Rear K digits from Numbers

When it is required to extract rear K digits from numbers, a simple list comprehension, the modulo operator and the ** operator are used. The modulo operator with 10**K effectively extracts the last K digits from any number.

How It Works

The formula number % (10**K) extracts the rear K digits because:

• 10**K creates a number with K+1 digits (e.g., 10³ = 1000)
• The modulo operation returns the remainder when dividing by this value
• This remainder is always less than 10**K, giving us exactly the last K digits

Example

Let's extract the last 3 digits from a list of numbers ?

my_list = [51645, 24567, 36743, 89452, 2122]

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

K = 3
print("The value of K is")
print(K)

my_result = [element % (10 ** K) for element in my_list]

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

The list is :
[51645, 24567, 36743, 89452, 2122]
The value of K is
3
The result is :
[645, 567, 743, 452, 122]

Different Values of K

Here's how different K values affect the same number ?

number = 12345

for k in range(1, 6):
    result = number % (10 ** k)
    print(f"Last {k} digits of {number}: {result}")

Last 1 digits of 12345: 5
Last 2 digits of 12345: 45
Last 3 digits of 12345: 345
Last 4 digits of 12345: 2345
Last 5 digits of 12345: 12345

Using a Function

You can create a reusable function for this operation ?

def extract_rear_digits(numbers, k):
    return [num % (10 ** k) for num in numbers]

# Test with different lists and K values
list1 = [12345, 67890, 111]
list2 = [987654, 123, 456789]

print("Extract last 2 digits:", extract_rear_digits(list1, 2))
print("Extract last 4 digits:", extract_rear_digits(list2, 4))

Extract last 2 digits: [45, 90, 11]
Extract last 4 digits: [7654, 123, 6789]

Conclusion

Use the modulo operator with 10**K to extract the rear K digits from numbers. This method works efficiently with list comprehensions for processing multiple numbers at once.