HackerRank Modified Kaprekar Numbers challenge

kaprekarNumbers.py

# A modified Kaprekar number is a positive whole number with a special property. If you square it, then split the number into two integers and sum those integers, you have the same value you started with.

# Consider a positive whole number  with  digits. We square  to arrive at a number that is either  digits long or  digits long. Split the string representation of the square into two parts,  and . The right hand part,  must be  digits long. The left is the remaining substring. Convert those two substrings back to integers, add them and see if you get .

# Example



# First calculate that . Split that into two strings and convert them back to integers  and . Test , so this is not a modified Kaprekar number. If , still , and . This gives us , the original .

# Note: r may have leading zeros.

# Here's an explanation from Wikipedia about the ORIGINAL Kaprekar Number (spot the difference!):

# In mathematics, a Kaprekar number for a given base is a non-negative integer, the representation of whose square in that base can be split into two parts that add up to the original number again. For instance, 45 is a Kaprekar number, because 45² = 2025 and 20+25 = 45.

# Given two positive integers  and  where  is lower than , write a program to print the modified Kaprekar numbers in the range between  and , inclusive. If no modified Kaprekar numbers exist in the given range, print INVALID RANGE.

# Function Description

# Complete the kaprekarNumbers function in the editor below.

# kaprekarNumbers has the following parameter(s):

# int p: the lower limit
# int q: the upper limit
# Prints

# It should print the list of modified Kaprekar numbers, space-separated on one line and in ascending order. If no modified Kaprekar numbers exist in the given range, print INVALID RANGE. No return value is required.

# Input Format

# The first line contains the lower integer limit .
# The second line contains the upper integer limit .

# Note: Your range should be inclusive of the limits.

# Constraints


# Sample Input

# STDIN   Function
# -----   --------
# 1       p = 1
# 100     q = 100
# Sample Output

# 1 9 45 55 99

# Explanation

# , , , , and  are the modified Kaprekar Numbers in the given range.


def kaprekarNumbers(p, q):
    # Write your code here
    k_num = []
    for i in range(p,q+1):
        square = i*i
        sqr_str = str(square)
        if len(sqr_str) > 2:
            if sqr_str[len(sqr_str)-len(str(i)):] != 0:
                    str_sum = int(sqr_str[len(sqr_str)-len(str(i)):]) + int(sqr_str[:len(sqr_str)-len(str(i))])
                    if str_sum == i:
                        k_num.append(i)
        else:
            num_sum = 0
            for num in sqr_str:
                num_sum += int(num)
            if num_sum == i:
                k_num.append(num_sum)
    if len(k_num) > 0:
        print(*k_num)
    else:
        print('INVALID RANGE')
kaprekarNumbers(1,100)

I get this error:
str_sum = int(sqr_str[:count]) + int(sqr_str[count:]) ValueError: invalid literal for int() with base 10:
why is this and what does it mean?