'list' object has no attribute 'replace'

I'm working on some code to encrypt a word into numbers from the polybius square, however I need the output to be the two numbers right next to each other e.g. 41 instead of a coordinate format (4, 1). Item.replace hasn't been working to get rid of the unnecessary characters, as it returns 'list' object has no attribute 'replace'. How can i get the output that i want?

import numpy as np
polybius_square = np.array([["a","b","c","d","e"],
                  ["f","g","h","i","j"],
                  ["k","l","m","n","o"],
                  ["p","q","r","s","t"],
                  ["u","v","w","x","y"]])
word = str(input("Enter a word"))
wordletters = list(word)
numbers = []
print(wordletters)
print(len(wordletters))
for count in range(0,len(wordletters)):
  solutions = np.argwhere(polybius_square == wordletters[count])
  solutions = solutions.tolist()
*  solutions = [item.replace(3, 10) for item in solutions]*
  print(solutions)
  numbers.append(solutions)
  print(numbers)
print(*numbers, sep=" ")

i tried a couple ways, but none let me get rid of any characters from the items in the lists.

Solution

The encryption algorithm isn't really the question. You have an np.array in this format:

import numpy as np

arr = np.array([[4, 3]])
print(arr)

Output:

[[4 3]]

and want the two-digit value:

num = arr[0][0] * 10 + arr[0][1]
print(num)

Output: