如何从只读属性改变到可写(已经zipfile.ZipFile()了的压缩文件)

import zipfile

z = zipfile.ZipFile("archive.zip")
info = z.getinfo('1.txt')
attr_w = info.external_attr & 254
offset = z.start_dir + info.header_offset + 38
z.close()

f = open("1.zip", "rb+")
f.seek(offset)
f.write(chr(attr_w))
f.close()