py7zr is a library and utility to support 7zip archive compression, decompression, encryption and decryption written by Python programming language.

Discussion Forum

You are welcome to join discussions on project forum/builtin-board at https://github.com/miurahr/py7zr/discussions

You can see announcements of new releases, questions and answers, and new feature ideas. When you doubt for usage of py7zr library with unclear manuals, please feel easy to raise question on forum.

Compression algorithms

py7zr supports algorithms and filters which lzma module and liblzma support, and supports BZip2 and Deflate that are implemented in python core libraries, It also supports ZStandard, Brotli and PPMd with third party libraries.

py7zr is also able to encrypt and decrypt data using 3rd party encryption library.

Supported algorithms

compress

LZMA2

Bzip2

Deflate

ZStandard

Brotli

Enhanced Deflate (Experimental)

A feature handling symbolic link is basically compatible with p7zip implementation, but not work with original 7-zip because the original does not implement the feature.

py7zr try checking symbolic links strictly and raise ValueError when bad link is requested, but it does not guarantee to block all the bad cases.

ZStandard and Brotli is not default methods of 7-zip, so these archives are considered not to be compatible with original 7-zip on windows/p7zip on linux/mac.

Enhanced Deflate is also known as DEFLATE64 ^TM that is a registered trademark of PKWARE, Inc.

Enhanced Deflate is tested only on CPython. It is disabled on PyPy.

You can install py7zr as usual other libraries using pip.

$ pip install py7zr

OR, alternatively using conda:

$ conda install -c conda-forge py7zr

Documents

User manuals

User Guide for latest version.

API Guide for latest version.

Manual for stable version.

Developer guide

Contribution guidelines for this project.

Contribution guidelines(html) for this project.

Code of conduct for this project.

Code of conduct(html) for this project.

7z file specification that py7zr stand on.

Decompression/Decryption

Here is a code snippet how to decompress some file in your application.

import py7zr
archive = py7zr.SevenZipFile('sample.7z', mode='r')
archive.extractall(path="/tmp")
archive.close()

You can also use ‘with’ block because py7zr provide context manager(v0.6 and later).

import py7zr
with py7zr.SevenZipFile('sample.7z', mode='r') as z:
    z.extractall()
with py7zr.SevenZipFile('target.7z', 'w') as z:
    z.writeall('./base_dir')

py7zr also supports extraction of single or selected files by ‘extract(targets=[‘file path’])’. Note: if you specify only a file but not a parent directory, it will fail.

import py7zr
import re
filter_pattern = re.compile(r'<your/target/file_and_directories/regex/expression>')
with py7zr.SevenZipFile('archive.7z', 'r') as archive:
    allfiles = archive.getnames()
    selective_files = [f for f in allfiles if filter_pattern.match(f)]
    archive.extract(targets=selective_files)

py7zr support an extraction of password protected archive.(v0.6 and later)

import py7zr
with py7zr.SevenZipFile('encrypted.7z', mode='r', password='secret') as z:
    z.extractall()

Compression/Encryption

Here is a code snippet how to produce archive.

import py7zr
with py7zr.SevenZipFile('target.7z', 'w') as archive:
    archive.writeall('/path/to/base_dir', 'base')

To create encrypted archive, please pass a password.

import py7zr
with py7zr.SevenZipFile('target.7z', 'w', password='secret') as archive:
    archive.writeall('/path/to/base_dir', 'base')

To create archive with algorithms such as zstandard, you can call with custom filter.

import py7zr
my_filters = [{"id": py7zr.FILTER_ZSTD}]
another_filters = [{"id": py7zr.FILTER_ARM}, {"id": py7zr.FILTER_LZMA2, "preset": 7}]
with py7zr.SevenZipFile('target.7z', 'w', filters=my_filters) as archive:
    archive.writeall('/path/to/base_dir', 'base')

shutil helper

py7zr also support shutil interface.

from py7zr import pack_7zarchive, unpack_7zarchive
import shutil
# register file format at first.
shutil.register_archive_format('7zip', pack_7zarchive, description='7zip archive')
shutil.register_unpack_format('7zip', ['.7z'], unpack_7zarchive)
# extraction
shutil.unpack_archive('test.7z', '/tmp')
# compression
shutil.make_archive('target', '7zip', 'src')

Requirements

py7zr uses a python3 standard lzma module for extraction and compression. The standard lzma module uses liblzma that support core compression algorithm of 7zip.

Minimum required version is Python 3.8.

py7zr tested on Linux, macOS, Windows and Ubuntu aarch64.

It hopefully works on M1 Mac too.

Recommended versions are:

CPython 3.8.0 and later.

PyPy3.8-7.3.8 and later.

Following fixes are included in these versions, and it is not fixed on python3.6.

BPO-21872 : LZMA library sometimes fails to decompress a file

PyPy3-3090 : lzma.LZMADecomporessor.decompress does not respect max_length

PyPy3-3242 : ‘_lzma_cffi’ has no function named ‘lzma_stream_encoder’

Following improvements are included in CPython 3.10

BPO-41486 : Faster bz2/lzma/zlib via new output buffering

Dependencies

There are several dependencies to support algorithms and CLI expressions.

Package

Purpose

PyCryptodomex

7zAES encryption

PyZstd

ZStandard compression

PyPPMd

PPMd compression

Brotli

Brotli compression (CPython)

BrotliCFFI

Brotli compression (PyPy)

inflate64

Enhanced deflate compression

pybcj

BCJ filters

multivolumefile

Multi-volume archive read/write

texttable

CLI formatter

Performance

You can find a compression and decompression benchmark results at [Github issue]( https://github.com/miurahr/py7zr/issues/297 ) and [wiki page]( https://github.com/miurahr/py7zr/wiki/Benchmarks )

py7zr works well, but slower than 7-zip and p7zip C/C++ implementation by several reasons. When compression/decompression speed is important, it is recommended to use these alternatives through subprocess.run python interface.

py7zr consumes some memory to decompress and compress data. It requires about 300MiB - 700MiB free memory to work well at least.

Use Cases

aqtinstall Another (unofficial) Qt (aqt) CLI Installer on multi-platforms.

PreNLP Preprocessing Library for Natural Language Processing

mlox a tool for sorting and analyzing Morrowind plugin load order

Security

Please find a Security Policy of this project.

Version 0.20.0, 0.19.0, 0.18.10 or before has a vulnerability for path traversal attack. Details are on “CVE-2022-44900: path traversal vulnerability in py7zr” disclose article .

Affected versions are vulnerable to Directory Traversal due to insufficient checks in the ‘py7zr.py’ and ‘helpers.py’ files

You are recommend to update immediately to version 0.20.2 or later

I really appreciate Mr. Matteo Cosentino for notification and corporation on security improvement.

License

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

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