How to fix this type error without type casting?

Traceback (most recent call last): File "D:/.Programming/Python/L6_Jiang_Tommy_tkj5216.py",line 54, in main() File "D:/.Programming/Python/L6_Jiang_Tommy_tkj5216.py",line 51, in main write_to_file("created_file.txt",test_lst) File "D:/.Programming/Python/L6_Jiang_Tommy_tkj5216.py",line 32, in write_to_file infile.write(lst+"")TypeError: can only concatenate list (not "str") to list

def write_to_file(filename,Ist): infile = open(filename,"w") if Ist == []: print("list is empty") else: for line in Ist: infile.write(Ist+" ") infile.close def append_to_file(filename,Ist): infile = open(filename,"a") if Ist ==[]: print("list is empty") else: for line in Ist: infile.write(Ist+" ") infile.close def main (): test_lst [1,2,3,4] addition_Ist=[5,6,7,8] empty_file("testfile.txt") create_file("created_file.txt","w") #result = read_file("read_from_this_file.txt") #result_line = read_file_lines("read_file_lines") write_to_file("created_file.txt",test_lst) append_to_file("created_file.txt",addition_Ist) main()