import os

def read_files(file_list):
    contents = []
    for filename in file_list:
        f = open(filename, 'r')
        data = f.read()
        contents.append(data)
    return contents

def write_output(data, filename):
    with open(filename, 'w') as f:
        f.write(data)

def append_to_file(filename, data):
    with open(filename, 'a') as f:
        f.write(data)