data = []
with open('file_src.py', 'r') as f:
    for line in f.readlines():
        data.append(line)
#
# process the data
#
with open('dest_file.py', 'w') as f:
    f.writelines(data)

# or
# write_data = ''.join(data)
# with open('dest_file.py', 'w') as f:
#     f.writelines(write_data )