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Pure python 7-zip library

Project description

logo py7zr – a 7z library on python

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


You can install py7zr as usual other libraries using pip.

$ pip install py7zr


User manuals

Developer guide

CLI Usage

You can run command script py7zr like as follows;

  • List archive contents
$ py7zr l test.7z
  • Extract archive
$ py7zr x test.7z
  • Extract archive with password
$ py7zr x -P test.7z
  password?: ****
  • Create and compress to archive
$ py7zr c target.7z test_dir
  • Create multi-volume archive
$ py7zr c -v 500k target.7z test_dir
  • Test archive
$ py7zr t test.7z
  • Append files to archive
$ py7zr a test.7z test_dir
  • Show information
$ py7zr i
  • Show version
$ py7zr --version

SevenZipFile Class Usage

py7zr is a library which can use in your python application.


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

import py7zr

archive = py7zr.SevenZipFile('sample.7z', mode='r')

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:

with py7zr.SevenZipFile('target.7z', 'w') as z:

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 SevenZipFile('archive.7z', 'r') as archive:
    allfiles = archive.getnames()
    selective_files = [f if filter_pattern.match(f) for f in allfiles]

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:


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_filter) as archive:
    archive.writeall('/path/to/base_dir', 'base')

shutil helper

py7zr also support shutil interface.

from py7zr import pack_7zarchvie, 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')

Required Python versions

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 3.6. Multi-volume archive creation is supported on Python 3.7 and later.

Version recommendations are:

  • CPython 3.7.5, CPython 3.8.0 and later.
  • PyPy3.6-7.2.0 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

Compression Methods supported

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

Supported algorithms are:

  • compress
    • LZMA2
    • LZMA
    • Bzip2
    • Deflate
    • Copy
    • PPMd
    • Zstandard
  • crypt
    • 7zAES
  • Filters
    • Delta
  • No supported
    • BCJ2
    • Deflate64
  • 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.


There are several dependencies to support algorithms and CLI expressions.

Package Purpose
Pycryptodome 7zAES encryption
ppmd-cffi PPMd compression
bcj-cffi BCJ filter
pyzstd ZStandard compression
texttable CLI


You can find a compression and decompression benchmark results at [Github issue]( and [wiki page](

Benchmarks are run with Github Actions manually triggered at [Github actions workflow](

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

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


  • Copyright (C) 2019-2021 Hiroshi Miura
  • pylzma Copyright (c) 2004-2015 by Joachim Bauch
  • 7-Zip Copyright (C) 1999-2010 Igor Pavlov
  • LZMA SDK Copyright (C) 1999-2010 Igor Pavlov

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


Test archive data, which affected a malware, have been existed from Aug, 2020 - 20, Jan, 2021!

All the git history is re-writed, so please remove your local and fork copy of the git repository, and clone again(if necessary)!

Problematic file is named issue_218.7z and issue_218_2.7z.

There is NO affected in library itself. and the test execution also does not extract the malware file. There is no problem when you install py7zr with pip command.

Release that has a clean source:

  • v0.11.3 and later
  • v0.10.2
  • v0.9.10
  • v0.9.4 and before

Py7zr ChangeLog

All notable changes to this project will be documented in this file.











  • Update release automation script.
  • Bump ppmd-cffi and bcj-cffi versions(#320)



  • Add option to specify multiprocessing instead of multi-threading. (#306)


  • Change Property Borg class to constant class(#319)
  • Reformat whole code with black.
  • Merge pyzstdfilter into
  • Lint codes by flake8/black.


  • README: description of dependencies.
  • ZStandard decompression on PyPy3



  • Fix of empty file archive(#305,#310)



  • Introduce writed() method that accept dict[name, BinaryIO](#302)


  • READ_BLOCKSIZE configurable on constructor(#307)
  • Use pyzstd for zstandard algorithm on CPython(#304)
  • Use bcj-cffi library for lzma+bcj performance(#303)
  • CLI: Fix getting module_name on 3.6.13(#308)



  • Add writestr() and writef() methods in SevenZipFile class.(#290,#293)
  • Add benchmark tests for compression algorithms(#295)
  • Track benchmark results on Github issue(#296)


  • Refactoring BCF Filter classes, and move to individual module.(#292)



  • PPMd and ZStandard is now one of default algorithms(#289)
  • Increment copyright year


  • Crash when append files to an empty files archive(#286)



  • Fix test failure when running on pypi source(#279)


  • Drop issue_218.7z test data wihch is reported a blackmoon trojan(#285)



  • Improve BCJ filter performance with LZMA1, ZStd compressions.


  • Fix to allow writing encrypted header(#280)
  • Avoid crash when creationtime is wrong or Unix epoch. (#275,#276)



  • PPMd: Use stream encoder/decoder instead of buffered one.
  • PPMd: Use ppmd-cffi@v0.3.1 and later.(#268)


  • PPMd compression/decompression support.(#255)
  • New API to set methods to set header encode mode, encode or encrypted.(#259)
  • Support Python 3.9.(#261)
  • Support arm64/aarch64 architecture on Linux.(#262)


  • Append mode cause error when target archive use LZMA2+BCJ.(#266)
  • Fix zstandard compression/decompression.(#258)


  • Drop support for python 3.5 which become end-of-line in Sept. 2020.



  • Fix exception when reading header which size is larger than buffer size (#252)



  • Compatibility test with python-libarchive-c/libarchive for compression(#247)
  • Document: express how to handle multi-volume archive (#243)
  • SevenZipFile.needs_password() method.(#208, #235)
  • CLI: Support append mode command line.(#228)
  • Support “APPEND” mode. User can open SevenZipFile() class with mode=’a’ (#227)


  • Calculate CRC32 of header without re-reading header from disk again.(#245)
  • read(), extract(): improve performance when specifying parts of archived file, by skipping rest of arcvhive when target file has extracted.(#239,#242)
  • read(), extract(): improve performance when specifying parts of archived file, by not running threads for unused compression blocks(folders).(#239,#242)
  • docs: improve API documentation.(#244)
  • setup: set minimum required python version as >=3.5
  • Compression will be happened when call write() not close() (#222, #226)
  • Handle file read/write in SevenZipCompressor/Decompressor class (#213)


  • Fix BCJ(x86) filter code with a missing logic which cause extraction error for certain data. (#249, #250)
  • Raise PasswordRequired when encrypted header without passing password (#234, #237)
  • CLI: don’t raise exception when password is wrong or not given.(#229)
  • Fix specification typo.
  • Catch exception in threading extraction(#218,#219)



  • Utilize max_length argument for each decompressor.(#210, #211)
  • Change READ_BUFFER_SIZE 32768 for python 3.7.5 and before.
  • Extend Buffer size when necessary.(#209)



  • Improve DecompressionChain.decompress() logics.(#207)


  • Fix BCJ filter for decompression that can cause infinite loop or wrong output.(#204,#205,#206)



  • BCJ Decoder/Encoder written by python.(#198, #199)
  • Support Bzip2, Defalte + BCJ(X86, PPC, ARM, ARMT, SPARC) (#199)
  • Add Copy method as an extraction only support.(#184)


  • Use large(1MB) read blocksize for Python 3.7.5 and later and PyPy 7.2.0 and later.
  • Set ZStandard compression as unsupported because of a bug with unknown reason.(#198)
  • Manage compression methods to handle whether decompressor requires coder[‘property’] or not.


  • Significantly improve decompress performance which is as same speed as v0.7.*. by updating buffer handling.
  • Fix decompression max_size to pass lzma module. Now it is as same as out_remaining.
  • Support LZMA+BCJ(X86, PPC, ARM, ARMT, SPARC) with alternative BCJ filter.(#198, #199)
  • Fix packinfo crc read and write (#187, #189)
  • Accept archive which Method ID is NULL(size=0)(#181, #182)
  • CLI: Does not crash when trying extract archive which use unsupported method(#183)



  • test: add test for #178 bug report the case of LZMA+BCJ as xfails.
  • File format specification: add ISO/IEC standard style specification document.
  • Support extra methods for archiveinfo() method.(#150)
  • test: unit tests for Sparc, ARMT and IA64 filters.
  • Support for PPC and ARM filters.
  • Support encryption(#145)
  • Export supported filter constants, such as FILTER_ZSTD(#145)


  • Improve README, documents and specifications.
  • Update password handling and drop get_password() helper (#162)
  • Enable encoded header and add more test with 7zip compatibility.(#164)
  • Refactoring SevenZipFile class internals. (#160)
  • Refactoring classes in compressor module. (#161)
  • Add ‘packinfo.crcs’ field digests data when creating archive.(#157) It help checking archive integrity without extraction.
  • CLI: help option to show py7zr version and python version.
  • Use importlib for performance improvement instead of pkg_resources module.
  • Documents: additional methods, filter examples.
  • CI configurations: Manage coverage with Coveralls.
  • Refactoring decompression classes to handle data precisely with folder.unpacksizes(#146)
  • Default compression mode is LZMA2+BCJ which is as same as 7zip and p7zip(#145)
  • Enhance encryption strength, IV is now 16 bytes, and generated with cryptodom.random module.(#145)
  • Refactoring compression algorythm related modules.


  • Now return correct header size by archiveinfo() method.(#169)
  • Disable adding CRC for encoded header packinfo.(#164)
  • Fix password leak/overwrite among SevenZipFile objects in a process.(#159) This can cause decryption error or encryption with unintended password.
  • Release password on close()
  • SevenZipFile.test() method now working properly. (#155)
  • Fix extraction error on python 3.5.(#151)
  • Support combination of filters(#145)
  • Compression of Delta, BZip2, ZStandard, and Deflate(#145)
  • Fix archived head by multiple filter specified.
  • Fix delta filter.
  • Working with BCJ filter.
  • Fix archiveinfo to provide proper names.


  • test: Drop some test case with large files.
  • Drop ArchiveProperty class: A field has already deprecated or not used.(#170)
  • Drop AntiFile property: a property has already deprecated or not used.
  • remove final_header definition.

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