Lib/zipfile/__init__.py (part 2)

Source:

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

This annotation covers writing and extracting from ZIP archives. See lib_zipfile_detail (if it exists) for ZipFile construction and reading.

Map

Lines	Symbol	Role
1-200	ZipInfo	Archive entry metadata: filename, date_time, compress_type, CRC
201-500	ZipFile.write	Add a file to the archive
501-800	ZipFile.writestr	Add bytes/str data directly
801-1100	ZipFile.open	Return a file-like object for reading an entry
1101-1400	ZipFile.extract, ZipFile.extractall	Extract to filesystem
1401-1700	_ZipWriteFile	Internal write file wrapper with compression
1701-2000	Central directory	Write end-of-central-directory record
2001-2400	ZIP64	Extra field for large files and many entries
2401-2800	Compression dispatch	zlib.compress, bz2.compress, lzma.compress

Reading

ZipInfo

# CPython: Lib/zipfile/__init__.py:190 ZipInfo
class ZipInfo:
    """Class with attributes describing each file in the ZIP archive."""
    __slots__ = (
        'orig_filename', 'filename', 'date_time', 'compress_type',
        'comment', 'extra', 'create_system', 'create_version',
        'extract_version', 'reserved', 'flag_bits', 'volume',
        'internal_attr', 'external_attr', 'compress_size',
        'file_size', '_raw_time', 'CRC', '_compressor', 'header_offset',
        '_end_offset',
    )

ZipFile.write

# CPython: Lib/zipfile/__init__.py:440 ZipFile.write
def write(self, filename, arcname=None, compress_type=None,
          compresslevel=None):
    """Put a file into the archive."""
    fname, arcname = self._get_codecs_name(filename, arcname)
    zinfo = ZipInfo.from_file(fname, arcname, strict_timestamps=self._strict_timestamps)
    if compress_type is not None:
        zinfo.compress_type = compress_type
    with open(fname, 'rb') as f:
        self._open_to_write(zinfo, force_zip64=False)
        while True:
            buf = f.read(1024 * 8)
            if not buf: break
            self._fileobj.write(buf)

_ZipWriteFile

# CPython: Lib/zipfile/__init__.py:1580 _ZipWriteFile.write
def write(self, data):
    nbytes = len(data)
    self._crc = crc32(data, self._crc)
    if self._compressor:
        data = self._compressor.compress(data)
    self._file_size += nbytes
    self._compress_size += len(data)
    self._fileobj.write(data)

CRC32 is computed incrementally as data is written.

Central directory

# CPython: Lib/zipfile/__init__.py:1820 ZipFile._write_end_record
def _write_end_record(self):
    """Write the central directory and end-of-central-directory record."""
    # Central directory entries
    for zinfo in self.filelist:
        self.fp.write(zinfo.FileHeader(zip64=...))
    # End-of-central-directory record
    centdir = struct.pack(structEndArchive, stringEndArchive,
                          0, 0, centcount, centcount, centsize, centoffset, 0)
    self.fp.write(centdir)

ZIP64 extension

# CPython: Lib/zipfile/__init__.py:2050 ZIP64
# Required when:
#   file_size    > 0xFFFFFFFF (4 GiB)
#   compress_size > 0xFFFFFFFF
#   header_offset > 0xFFFFFFFF
#   total entries > 0xFFFF
# Uses Zip64 extra field (tag 0x0001) with 64-bit values

gopy notes

zipfile is pure Python and importable when zlib, bz2, lzma, struct, io, os, time, and binascii work. The compression types map to compress/zlib, compress/bzip2, and compress/lzma in Go. CRC32 uses hash/crc32.ChecksumIEEE.