Lib/zipfile/__init__.py (part 3)

Source:

cpython 3.14 @ ab2d84fe1023/Lib/zipfile/__init__.py ↗

This annotation covers reading and writing ZIP entries. See lib_zipfile2_detail for ZipFile.__init__, namelist, infolist, and the central directory.

Map

Lines	Symbol	Role
1-80	ZipFile.open	Open a member as a file-like object
81-180	ZipFile.read	Read a member's bytes
181-260	ZipFile.extract / extractall	Extract member(s) to filesystem
261-360	ZipFile.write	Add a file to the archive
361-500	Compression methods	ZIP_STORED, ZIP_DEFLATED, ZIP_BZIP2, ZIP_LZMA

Reading

ZipFile.open

# CPython: Lib/zipfile/__init__.py:1380 ZipFile.open
def open(self, name, mode="r", pwd=None, *, force_zip64=False):
    if isinstance(name, ZipInfo):
        zinfo = name
    else:
        zinfo = self.getinfo(name)
    if mode == 'r':
        return self._open_to_read(zinfo, pwd)
    elif mode == 'w':
        return self._open_to_write(zinfo, force_zip64=force_zip64)

def _open_to_read(self, zinfo, pwd):
    self._filerefcnt += 1
    zef_file = _SharedFile(self.fp, zinfo.header_offset, ...)
    return ZipExtFile(zef_file, 'rb', zinfo, pwd, True)

ZipFile.open('data.json') returns a ZipExtFile that decompresses on-the-fly. _SharedFile wraps the underlying file pointer, seeking to the member's data offset. Multiple members can be open simultaneously (the shared file handles concurrent seeks via locks).

ZipFile.write

# CPython: Lib/zipfile/__init__.py:1660 ZipFile.write
def write(self, filename, arcname=None, compress_type=None,
          compresslevel=None):
    fname, arcname = self._get_codecs(filename, arcname)
    zinfo = ZipInfo.from_file(fname, arcname, ...)
    if compress_type is not None:
        zinfo.compress_type = compress_type
    with open(fname, 'rb') as f:
        self.writestr(zinfo, f.read(), compress_type, compresslevel)

write creates a ZipInfo from the file's stat result, then calls writestr. The local file header is written first, then the (possibly compressed) data. The central directory entry is appended to self.filelist.

Compression methods

Method	Value	Module
ZIP_STORED	0	No compression
ZIP_DEFLATED	8	zlib.compress
ZIP_BZIP2	12	bz2.compress
ZIP_LZMA	14	lzma.compress

Default is ZIP_STORED. ZIP_DEFLATED requires zlib. compress_type can be set per-file, overriding the archive default.

gopy notes

ZipFile.open is module/zipfile.ZipFileOpen in module/zipfile/module.go. It uses Go's archive/zip for reading. ZipFile.write uses zip.Writer.Create. ZIP_DEFLATED maps to zip.Deflate. Custom compress types are handled by registering decoders.