read from one file and write to another file line by line

def copy(input_file, output_file):
    in_file = open(input_file, 'r')
    out_file = open(output_file, 'w')
    
    for line in in_file:
        out_file.write(line)
        
    in_file.close()
    out_file.close()
    
    
copy('input.txt', 'output.txt')