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:mod:`zipfile` --- Work with ZIP archives
=========================================
.. module:: zipfile
:synopsis: Read and write ZIP-format archive files.
.. moduleauthor:: James C. Ahlstrom <jim@interet.com>
.. sectionauthor:: James C. Ahlstrom <jim@interet.com>
**Source code:** :source:`Lib/zipfile.py`
--------------
The ZIP file format is a common archive and compression standard. This module
provides tools to create, read, write, append, and list a ZIP file. Any
advanced use of this module will require an understanding of the format, as
defined in `PKZIP Application Note`_.
This module does not currently handle multi-disk ZIP files.
It can handle ZIP files that use the ZIP64 extensions
(that is ZIP files that are more than 4 GiB in size). It supports
decryption of encrypted files in ZIP archives, but it currently cannot
create an encrypted file. Decryption is extremely slow as it is
implemented in native Python rather than C.
The module defines the following items:
.. exception:: BadZipFile
The error raised for bad ZIP files.
.. versionadded:: 3.2
.. exception:: BadZipfile
Alias of :exc:`BadZipFile`, for compatibility with older Python versions.
.. deprecated:: 3.2
.. exception:: LargeZipFile
The error raised when a ZIP file would require ZIP64 functionality but that has
not been enabled.
.. class:: ZipFile
:noindex:
The class for reading and writing ZIP files. See section
:ref:`zipfile-objects` for constructor details.
.. class:: Path
:noindex:
A pathlib-compatible wrapper for zip files. See section
:ref:`path-objects` for details.
.. versionadded:: 3.8
.. class:: PyZipFile
:noindex:
Class for creating ZIP archives containing Python libraries.
.. class:: ZipInfo(filename='NoName', date_time=(1980,1,1,0,0,0))
Class used to represent information about a member of an archive. Instances
of this class are returned by the :meth:`.getinfo` and :meth:`.infolist`
methods of :class:`ZipFile` objects. Most users of the :mod:`zipfile` module
will not need to create these, but only use those created by this
module. *filename* should be the full name of the archive member, and
*date_time* should be a tuple containing six fields which describe the time
of the last modification to the file; the fields are described in section
:ref:`zipinfo-objects`.
.. function:: is_zipfile(filename)
Returns ``True`` if *filename* is a valid ZIP file based on its magic number,
otherwise returns ``False``. *filename* may be a file or file-like object too.
.. versionchanged:: 3.1
Support for file and file-like objects.
.. data:: ZIP_STORED
The numeric constant for an uncompressed archive member.
.. data:: ZIP_DEFLATED
The numeric constant for the usual ZIP compression method. This requires the
:mod:`zlib` module.
.. data:: ZIP_BZIP2
The numeric constant for the BZIP2 compression method. This requires the
:mod:`bz2` module.
.. versionadded:: 3.3
.. data:: ZIP_LZMA
The numeric constant for the LZMA compression method. This requires the
:mod:`lzma` module.
.. versionadded:: 3.3
.. note::
The ZIP file format specification has included support for bzip2 compression
since 2001, and for LZMA compression since 2006. However, some tools
(including older Python releases) do not support these compression
methods, and may either refuse to process the ZIP file altogether,
or fail to extract individual files.
.. seealso::
`PKZIP Application Note`_
Documentation on the ZIP file format by Phil Katz, the creator of the format and
algorithms used.
`Info-ZIP Home Page <http://www.info-zip.org/>`_
Information about the Info-ZIP project's ZIP archive programs and development
libraries.
.. _zipfile-objects:
ZipFile Objects
---------------
.. class:: ZipFile(file, mode='r', compression=ZIP_STORED, allowZip64=True, \
compresslevel=None, *, strict_timestamps=True)
Open a ZIP file, where *file* can be a path to a file (a string), a
file-like object or a :term:`path-like object`.
The *mode* parameter should be ``'r'`` to read an existing
file, ``'w'`` to truncate and write a new file, ``'a'`` to append to an
existing file, or ``'x'`` to exclusively create and write a new file.
If *mode* is ``'x'`` and *file* refers to an existing file,
a :exc:`FileExistsError` will be raised.
If *mode* is ``'a'`` and *file* refers to an existing ZIP
file, then additional files are added to it. If *file* does not refer to a
ZIP file, then a new ZIP archive is appended to the file. This is meant for
adding a ZIP archive to another file (such as :file:`python.exe`). If
*mode* is ``'a'`` and the file does not exist at all, it is created.
If *mode* is ``'r'`` or ``'a'``, the file should be seekable.
*compression* is the ZIP compression method to use when writing the archive,
and should be :const:`ZIP_STORED`, :const:`ZIP_DEFLATED`,
:const:`ZIP_BZIP2` or :const:`ZIP_LZMA`; unrecognized
values will cause :exc:`NotImplementedError` to be raised. If
:const:`ZIP_DEFLATED`, :const:`ZIP_BZIP2` or :const:`ZIP_LZMA` is specified
but the corresponding module (:mod:`zlib`, :mod:`bz2` or :mod:`lzma`) is not
available, :exc:`RuntimeError` is raised. The default is :const:`ZIP_STORED`.
If *allowZip64* is ``True`` (the default) zipfile will create ZIP files that
use the ZIP64 extensions when the zipfile is larger than 4 GiB. If it is
``false`` :mod:`zipfile` will raise an exception when the ZIP file would
require ZIP64 extensions.
The *compresslevel* parameter controls the compression level to use when
writing files to the archive.
When using :const:`ZIP_STORED` or :const:`ZIP_LZMA` it has no effect.
When using :const:`ZIP_DEFLATED` integers ``0`` through ``9`` are accepted
(see :class:`zlib <zlib.compressobj>` for more information).
When using :const:`ZIP_BZIP2` integers ``1`` through ``9`` are accepted
(see :class:`bz2 <bz2.BZ2File>` for more information).
The *strict_timestamps* argument, when set to ``False``, allows to
zip files older than 1980-01-01 at the cost of setting the
timestamp to 1980-01-01.
Similar behavior occurs with files newer than 2107-12-31,
the timestamp is also set to the limit.
If the file is created with mode ``'w'``, ``'x'`` or ``'a'`` and then
:meth:`closed <close>` without adding any files to the archive, the appropriate
ZIP structures for an empty archive will be written to the file.
ZipFile is also a context manager and therefore supports the
:keyword:`with` statement. In the example, *myzip* is closed after the
:keyword:`!with` statement's suite is finished---even if an exception occurs::
with ZipFile('spam.zip', 'w') as myzip:
myzip.write('eggs.txt')
.. versionadded:: 3.2
Added the ability to use :class:`ZipFile` as a context manager.
.. versionchanged:: 3.3
Added support for :mod:`bzip2 <bz2>` and :mod:`lzma` compression.
.. versionchanged:: 3.4
ZIP64 extensions are enabled by default.
.. versionchanged:: 3.5
Added support for writing to unseekable streams.
Added support for the ``'x'`` mode.
.. versionchanged:: 3.6
Previously, a plain :exc:`RuntimeError` was raised for unrecognized
compression values.
.. versionchanged:: 3.6.2
The *file* parameter accepts a :term:`path-like object`.
.. versionchanged:: 3.7
Add the *compresslevel* parameter.
.. versionadded:: 3.8
The *strict_timestamps* keyword-only argument
.. method:: ZipFile.close()
Close the archive file. You must call :meth:`close` before exiting your program
or essential records will not be written.
.. method:: ZipFile.getinfo(name)
Return a :class:`ZipInfo` object with information about the archive member
*name*. Calling :meth:`getinfo` for a name not currently contained in the
archive will raise a :exc:`KeyError`.
.. method:: ZipFile.infolist()
Return a list containing a :class:`ZipInfo` object for each member of the
archive. The objects are in the same order as their entries in the actual ZIP
file on disk if an existing archive was opened.
.. method:: ZipFile.namelist()
Return a list of archive members by name.
.. method:: ZipFile.open(name, mode='r', pwd=None, *, force_zip64=False)
Access a member of the archive as a binary file-like object. *name*
can be either the name of a file within the archive or a :class:`ZipInfo`
object. The *mode* parameter, if included, must be ``'r'`` (the default)
or ``'w'``. *pwd* is the password used to decrypt encrypted ZIP files.
:meth:`~ZipFile.open` is also a context manager and therefore supports the
:keyword:`with` statement::
with ZipFile('spam.zip') as myzip:
with myzip.open('eggs.txt') as myfile:
print(myfile.read())
With *mode* ``'r'`` the file-like object
(``ZipExtFile``) is read-only and provides the following methods:
:meth:`~io.BufferedIOBase.read`, :meth:`~io.IOBase.readline`,
:meth:`~io.IOBase.readlines`, :meth:`~io.IOBase.seek`,
:meth:`~io.IOBase.tell`, :meth:`__iter__`, :meth:`~iterator.__next__`.
These objects can operate independently of the ZipFile.
With ``mode='w'``, a writable file handle is returned, which supports the
:meth:`~io.BufferedIOBase.write` method. While a writable file handle is open,
attempting to read or write other files in the ZIP file will raise a
:exc:`ValueError`.
When writing a file, if the file size is not known in advance but may exceed
2 GiB, pass ``force_zip64=True`` to ensure that the header format is
capable of supporting large files. If the file size is known in advance,
construct a :class:`ZipInfo` object with :attr:`~ZipInfo.file_size` set, and
use that as the *name* parameter.
.. note::
The :meth:`.open`, :meth:`read` and :meth:`extract` methods can take a filename
or a :class:`ZipInfo` object. You will appreciate this when trying to read a
ZIP file that contains members with duplicate names.
.. versionchanged:: 3.6
Removed support of ``mode='U'``. Use :class:`io.TextIOWrapper` for reading
compressed text files in :term:`universal newlines` mode.
.. versionchanged:: 3.6
:meth:`open` can now be used to write files into the archive with the
``mode='w'`` option.
.. versionchanged:: 3.6
Calling :meth:`.open` on a closed ZipFile will raise a :exc:`ValueError`.
Previously, a :exc:`RuntimeError` was raised.
.. method:: ZipFile.extract(member, path=None, pwd=None)
Extract a member from the archive to the current working directory; *member*
must be its full name or a :class:`ZipInfo` object. Its file information is
extracted as accurately as possible. *path* specifies a different directory
to extract to. *member* can be a filename or a :class:`ZipInfo` object.
*pwd* is the password used for encrypted files.
Returns the normalized path created (a directory or new file).
.. note::
If a member filename is an absolute path, a drive/UNC sharepoint and
leading (back)slashes will be stripped, e.g.: ``///foo/bar`` becomes
``foo/bar`` on Unix, and ``C:\foo\bar`` becomes ``foo\bar`` on Windows.
And all ``".."`` components in a member filename will be removed, e.g.:
``../../foo../../ba..r`` becomes ``foo../ba..r``. On Windows illegal
characters (``:``, ``<``, ``>``, ``|``, ``"``, ``?``, and ``*``)
replaced by underscore (``_``).
.. versionchanged:: 3.6
Calling :meth:`extract` on a closed ZipFile will raise a
:exc:`ValueError`. Previously, a :exc:`RuntimeError` was raised.
.. versionchanged:: 3.6.2
The *path* parameter accepts a :term:`path-like object`.
.. method:: ZipFile.extractall(path=None, members=None, pwd=None)
Extract all members from the archive to the current working directory. *path*
specifies a different directory to extract to. *members* is optional and must
be a subset of the list returned by :meth:`namelist`. *pwd* is the password
used for encrypted files.
.. warning::
Never extract archives from untrusted sources without prior inspection.
It is possible that files are created outside of *path*, e.g. members
that have absolute filenames starting with ``"/"`` or filenames with two
dots ``".."``. This module attempts to prevent that.
See :meth:`extract` note.
.. versionchanged:: 3.6
Calling :meth:`extractall` on a closed ZipFile will raise a
:exc:`ValueError`. Previously, a :exc:`RuntimeError` was raised.
.. versionchanged:: 3.6.2
The *path* parameter accepts a :term:`path-like object`.
.. method:: ZipFile.printdir()
Print a table of contents for the archive to ``sys.stdout``.
.. method:: ZipFile.setpassword(pwd)
Set *pwd* as default password to extract encrypted files.
.. method:: ZipFile.read(name, pwd=None)
Return the bytes of the file *name* in the archive. *name* is the name of the
file in the archive, or a :class:`ZipInfo` object. The archive must be open for
read or append. *pwd* is the password used for encrypted files and, if specified,
it will override the default password set with :meth:`setpassword`. Calling
:meth:`read` on a ZipFile that uses a compression method other than
:const:`ZIP_STORED`, :const:`ZIP_DEFLATED`, :const:`ZIP_BZIP2` or
:const:`ZIP_LZMA` will raise a :exc:`NotImplementedError`. An error will also
be raised if the corresponding compression module is not available.
.. versionchanged:: 3.6
Calling :meth:`read` on a closed ZipFile will raise a :exc:`ValueError`.
Previously, a :exc:`RuntimeError` was raised.
.. method:: ZipFile.testzip()
Read all the files in the archive and check their CRC's and file headers.
Return the name of the first bad file, or else return ``None``.
.. versionchanged:: 3.6
Calling :meth:`testzip` on a closed ZipFile will raise a
:exc:`ValueError`. Previously, a :exc:`RuntimeError` was raised.
.. method:: ZipFile.write(filename, arcname=None, compress_type=None, \
compresslevel=None)
Write the file named *filename* to the archive, giving it the archive name
*arcname* (by default, this will be the same as *filename*, but without a drive
letter and with leading path separators removed). If given, *compress_type*
overrides the value given for the *compression* parameter to the constructor for
the new entry. Similarly, *compresslevel* will override the constructor if
given.
The archive must be open with mode ``'w'``, ``'x'`` or ``'a'``.
.. note::
Archive names should be relative to the archive root, that is, they should not
start with a path separator.
.. note::
If ``arcname`` (or ``filename``, if ``arcname`` is not given) contains a null
byte, the name of the file in the archive will be truncated at the null byte.
.. versionchanged:: 3.6
Calling :meth:`write` on a ZipFile created with mode ``'r'`` or
a closed ZipFile will raise a :exc:`ValueError`. Previously,
a :exc:`RuntimeError` was raised.
.. method:: ZipFile.writestr(zinfo_or_arcname, data, compress_type=None, \
compresslevel=None)
Write a file into the archive. The contents is *data*, which may be either
a :class:`str` or a :class:`bytes` instance; if it is a :class:`str`,
it is encoded as UTF-8 first. *zinfo_or_arcname* is either the file
name it will be given in the archive, or a :class:`ZipInfo` instance. If it's
an instance, at least the filename, date, and time must be given. If it's a
name, the date and time is set to the current date and time.
The archive must be opened with mode ``'w'``, ``'x'`` or ``'a'``.
If given, *compress_type* overrides the value given for the *compression*
parameter to the constructor for the new entry, or in the *zinfo_or_arcname*
(if that is a :class:`ZipInfo` instance). Similarly, *compresslevel* will
override the constructor if given.
.. note::
When passing a :class:`ZipInfo` instance as the *zinfo_or_arcname* parameter,
the compression method used will be that specified in the *compress_type*
member of the given :class:`ZipInfo` instance. By default, the
:class:`ZipInfo` constructor sets this member to :const:`ZIP_STORED`.
.. versionchanged:: 3.2
The *compress_type* argument.
.. versionchanged:: 3.6
Calling :meth:`writestr` on a ZipFile created with mode ``'r'`` or
a closed ZipFile will raise a :exc:`ValueError`. Previously,
a :exc:`RuntimeError` was raised.
The following data attributes are also available:
.. attribute:: ZipFile.filename
Name of the ZIP file.
.. attribute:: ZipFile.debug
The level of debug output to use. This may be set from ``0`` (the default, no
output) to ``3`` (the most output). Debugging information is written to
``sys.stdout``.
.. attribute:: ZipFile.comment
The comment associated with the ZIP file as a :class:`bytes` object.
If assigning a comment to a
:class:`ZipFile` instance created with mode ``'w'``, ``'x'`` or ``'a'``,
it should be no longer than 65535 bytes. Comments longer than this will be
truncated.
.. _path-objects:
Path Objects
------------
.. class:: Path(root, at='')
Construct a Path object from a ``root`` zipfile (which may be a
:class:`ZipFile` instance or ``file`` suitable for passing to
the :class:`ZipFile` constructor).
``at`` specifies the location of this Path within the zipfile,
e.g. 'dir/file.txt', 'dir/', or ''. Defaults to the empty string,
indicating the root.
Path objects expose the following features of :mod:`pathlib.Path`
objects:
Path objects are traversable using the ``/`` operator.
.. attribute:: Path.name
The final path component.
.. method:: Path.open(mode='r', *, pwd, **)
Invoke :meth:`ZipFile.open` on the current path.
Allows opening for read or write, text or binary
through supported modes: 'r', 'w', 'rb', 'wb'.
Positional and keyword arguments are passed through to
:class:`io.TextIOWrapper` when opened as text and
ignored otherwise.
``pwd`` is the ``pwd`` parameter to
:meth:`ZipFile.open`.
.. versionchanged:: 3.9
Added support for text and binary modes for open. Default
mode is now text.
.. method:: Path.iterdir()
Enumerate the children of the current directory.
.. method:: Path.is_dir()
Return ``True`` if the current context references a directory.
.. method:: Path.is_file()
Return ``True`` if the current context references a file.
.. method:: Path.exists()
Return ``True`` if the current context references a file or
directory in the zip file.
.. method:: Path.read_text(*, **)
Read the current file as unicode text. Positional and
keyword arguments are passed through to
:class:`io.TextIOWrapper` (except ``buffer``, which is
implied by the context).
.. method:: Path.read_bytes()
Read the current file as bytes.
.. _pyzipfile-objects:
PyZipFile Objects
-----------------
The :class:`PyZipFile` constructor takes the same parameters as the
:class:`ZipFile` constructor, and one additional parameter, *optimize*.
.. class:: PyZipFile(file, mode='r', compression=ZIP_STORED, allowZip64=True, \
optimize=-1)
.. versionadded:: 3.2
The *optimize* parameter.
.. versionchanged:: 3.4
ZIP64 extensions are enabled by default.
Instances have one method in addition to those of :class:`ZipFile` objects:
.. method:: PyZipFile.writepy(pathname, basename='', filterfunc=None)
Search for files :file:`\*.py` and add the corresponding file to the
archive.
If the *optimize* parameter to :class:`PyZipFile` was not given or ``-1``,
the corresponding file is a :file:`\*.pyc` file, compiling if necessary.
If the *optimize* parameter to :class:`PyZipFile` was ``0``, ``1`` or
``2``, only files with that optimization level (see :func:`compile`) are
added to the archive, compiling if necessary.
If *pathname* is a file, the filename must end with :file:`.py`, and
just the (corresponding :file:`\*.pyc`) file is added at the top level
(no path information). If *pathname* is a file that does not end with
:file:`.py`, a :exc:`RuntimeError` will be raised. If it is a directory,
and the directory is not a package directory, then all the files
:file:`\*.pyc` are added at the top level. If the directory is a
package directory, then all :file:`\*.pyc` are added under the package
name as a file path, and if any subdirectories are package directories,
all of these are added recursively in sorted order.
*basename* is intended for internal use only.
*filterfunc*, if given, must be a function taking a single string
argument. It will be passed each path (including each individual full
file path) before it is added to the archive. If *filterfunc* returns a
false value, the path will not be added, and if it is a directory its
contents will be ignored. For example, if our test files are all either
in ``test`` directories or start with the string ``test_``, we can use a
*filterfunc* to exclude them::
>>> zf = PyZipFile('myprog.zip')
>>> def notests(s):
... fn = os.path.basename(s)
... return (not (fn == 'test' or fn.startswith('test_')))
>>> zf.writepy('myprog', filterfunc=notests)
The :meth:`writepy` method makes archives with file names like
this::
string.pyc # Top level name
test/__init__.pyc # Package directory
test/testall.pyc # Module test.testall
test/bogus/__init__.pyc # Subpackage directory
test/bogus/myfile.pyc # Submodule test.bogus.myfile
.. versionadded:: 3.4
The *filterfunc* parameter.
.. versionchanged:: 3.6.2
The *pathname* parameter accepts a :term:`path-like object`.
.. versionchanged:: 3.7
Recursion sorts directory entries.
.. _zipinfo-objects:
ZipInfo Objects
---------------
Instances of the :class:`ZipInfo` class are returned by the :meth:`.getinfo` and
:meth:`.infolist` methods of :class:`ZipFile` objects. Each object stores
information about a single member of the ZIP archive.
There is one classmethod to make a :class:`ZipInfo` instance for a filesystem
file:
.. classmethod:: ZipInfo.from_file(filename, arcname=None, *, \
strict_timestamps=True)
Construct a :class:`ZipInfo` instance for a file on the filesystem, in
preparation for adding it to a zip file.
*filename* should be the path to a file or directory on the filesystem.
If *arcname* is specified, it is used as the name within the archive.
If *arcname* is not specified, the name will be the same as *filename*, but
with any drive letter and leading path separators removed.
The *strict_timestamps* argument, when set to ``False``, allows to
zip files older than 1980-01-01 at the cost of setting the
timestamp to 1980-01-01.
Similar behavior occurs with files newer than 2107-12-31,
the timestamp is also set to the limit.
.. versionadded:: 3.6
.. versionchanged:: 3.6.2
The *filename* parameter accepts a :term:`path-like object`.
.. versionadded:: 3.8
The *strict_timestamps* keyword-only argument
Instances have the following methods and attributes:
.. method:: ZipInfo.is_dir()
Return ``True`` if this archive member is a directory.
This uses the entry's name: directories should always end with ``/``.
.. versionadded:: 3.6
.. attribute:: ZipInfo.filename
Name of the file in the archive.
.. attribute:: ZipInfo.date_time
The time and date of the last modification to the archive member. This is a
tuple of six values:
+-------+--------------------------+
| Index | Value |
+=======+==========================+
| ``0`` | Year (>= 1980) |
+-------+--------------------------+
| ``1`` | Month (one-based) |
+-------+--------------------------+
| ``2`` | Day of month (one-based) |
+-------+--------------------------+
| ``3`` | Hours (zero-based) |
+-------+--------------------------+
| ``4`` | Minutes (zero-based) |
+-------+--------------------------+
| ``5`` | Seconds (zero-based) |
+-------+--------------------------+
.. note::
The ZIP file format does not support timestamps before 1980.
.. attribute:: ZipInfo.compress_type
Type of compression for the archive member.
.. attribute:: ZipInfo.comment
Comment for the individual archive member as a :class:`bytes` object.
.. attribute:: ZipInfo.extra
Expansion field data. The `PKZIP Application Note`_ contains
some comments on the internal structure of the data contained in this
:class:`bytes` object.
.. attribute:: ZipInfo.create_system
System which created ZIP archive.
.. attribute:: ZipInfo.create_version
PKZIP version which created ZIP archive.
.. attribute:: ZipInfo.extract_version
PKZIP version needed to extract archive.
.. attribute:: ZipInfo.reserved
Must be zero.
.. attribute:: ZipInfo.flag_bits
ZIP flag bits.
.. attribute:: ZipInfo.volume
Volume number of file header.
.. attribute:: ZipInfo.internal_attr
Internal attributes.
.. attribute:: ZipInfo.external_attr
External file attributes.
.. attribute:: ZipInfo.header_offset
Byte offset to the file header.
.. attribute:: ZipInfo.CRC
CRC-32 of the uncompressed file.
.. attribute:: ZipInfo.compress_size
Size of the compressed data.
.. attribute:: ZipInfo.file_size
Size of the uncompressed file.
.. _zipfile-commandline:
.. program:: zipfile
Command-Line Interface
----------------------
The :mod:`zipfile` module provides a simple command-line interface to interact
with ZIP archives.
If you want to create a new ZIP archive, specify its name after the :option:`-c`
option and then list the filename(s) that should be included:
.. code-block:: shell-session
$ python -m zipfile -c monty.zip spam.txt eggs.txt
Passing a directory is also acceptable:
.. code-block:: shell-session
$ python -m zipfile -c monty.zip life-of-brian_1979/
If you want to extract a ZIP archive into the specified directory, use
the :option:`-e` option:
.. code-block:: shell-session
$ python -m zipfile -e monty.zip target-dir/
For a list of the files in a ZIP archive, use the :option:`-l` option:
.. code-block:: shell-session
$ python -m zipfile -l monty.zip
Command-line options
~~~~~~~~~~~~~~~~~~~~
.. cmdoption:: -l <zipfile>
--list <zipfile>
List files in a zipfile.
.. cmdoption:: -c <zipfile> <source1> ... <sourceN>
--create <zipfile> <source1> ... <sourceN>
Create zipfile from source files.
.. cmdoption:: -e <zipfile> <output_dir>
--extract <zipfile> <output_dir>
Extract zipfile into target directory.
.. cmdoption:: -t <zipfile>
--test <zipfile>
Test whether the zipfile is valid or not.
Decompression pitfalls
----------------------
The extraction in zipfile module might fail due to some pitfalls listed below.
From file itself
~~~~~~~~~~~~~~~~
Decompression may fail due to incorrect password / CRC checksum / ZIP format or
unsupported compression method / decryption.
File System limitations
~~~~~~~~~~~~~~~~~~~~~~~
Exceeding limitations on different file systems can cause decompression failed.
Such as allowable characters in the directory entries, length of the file name,
length of the pathname, size of a single file, and number of files, etc.
Resources limitations
~~~~~~~~~~~~~~~~~~~~~
The lack of memory or disk volume would lead to decompression
failed. For example, decompression bombs (aka `ZIP bomb`_)
apply to zipfile library that can cause disk volume exhaustion.
Interruption
~~~~~~~~~~~~
Interruption during the decompression, such as pressing control-C or killing the
decompression process may result in incomplete decompression of the archive.
Default behaviors of extraction
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Not knowing the default extraction behaviors
can cause unexpected decompression results.
For example, when extracting the same archive twice,
it overwrites files without asking.
.. _ZIP bomb: https://en.wikipedia.org/wiki/Zip_bomb
.. _PKZIP Application Note: https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT
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