[python] How to resolve TypeError: can only concatenate str (not "int") to str

Change secret_string += str(chr(char + 7429146))

To secret_string += chr(ord(char) + 7429146)

ord() converts the character to its Unicode integer equivalent. chr() then converts this integer into its Unicode character equivalent.

Also, 7429146 is too big of a number, it should be less than 1114111