pyfakefs Release Notes

The released versions correspond to PyPi releases.

Unreleased

Version 4.5.6 (2022-03-17)

Fixes a regression which broke tests with older pytest versions (< 3.9).

Changes

  • minimum supported pytest version is now 3.0 (older versions do not work properly with current Python versions)

Fixes

  • only skip _pytest.pathlib in pytest versions where it is actually present (see #669)

Infrastructure

  • add tests with different pytest versions, starting with 3.0

Version 4.5.5 (2022-02-14)

Bugfix release, needed for compatibility with pytest 7.0.

Fixes

  • correctly handle file system space for files opened in write mode (see #660)
  • correctly handle reading/writing pipes via file (see #661)
  • disallow encoding argument on binary open() (see #664)
  • fixed compatibility issue with pytest 7.0.0 (see #666)

Version 4.5.4 (2022-01-12)

Minor bugfix release.

Fixes

  • added missing mocked functions for fake pipe (see #650)
  • fixed some bytes warnings (see #651)

Version 4.5.3 (2021-11-08)

Reverts a change in the previous release that could cause a regression.

Changes

  • os.listdir, os.scandir and pathlib.Path.listdir now return the directory list in a random order only if explicitly configured in the file system (use fs.shuffle_listdir_results = True with fs being the file system). In a future version, the default may be changed to better reflect the real filesystem behavior (see #647)

Version 4.5.2 (2021-11-07)

This is a bugfix release.

Changes

  • os.listdir, os.scandir and pathlib.Path.listdir now return the directory list in a random order (see #638)
  • the fcntl module under Unix is now mocked, e.g. all functions have no effect (this may be changed in the future if needed, see #645)

Fixes

  • fixed handling of alternative path separator in os.path.split, os.path.splitdrive and glob.glob (see #632)
  • fixed handling of failed rename due to permission error (see #643)

Version 4.5.1 (2021-08-29)

This is a bugfix release.

Fixes

  • added handling of path-like where missing
  • improved handling of str/bytes paths
  • suppress all warnings while inspecting loaded modules (see #614)
  • do not import pandas and related modules if it is not patched (see #627)
  • handle pathlib.Path.owner() and pathlib.Path.group by returning the current user/group name (see #629)
  • fixed handling of use_known_patches=False (could cause an exception)
  • removed Python 3.5 from metadata to disable installation for that version (see #615)

Infrastructure

  • added test dependency check (see #608)
  • skip tests failing with ASCII locale (see #623)

Version 4.5.0 (2021-06-04)

Adds some support for Python 3.10 and basic type checking.

Note: This version has been yanked from PyPi as it erroneously allowed installation under Python 3.5.

New Features

  • added support for some Python 3.10 features:
    • new method pathlib.Path.hardlink_to
    • new newline argument in pathlib.Path.write_text
    • new follow_symlinks argument in pathlib.Path.stat and pathlib.Path.chmod
    • new ‘strict’ argument in os.path.realpath

Changes

  • Python 3.5 has reached its end of life in September 2020 and is no longer supported
  • pathlib2 is still supported, but considered to have the same functionality as pathlib and is no longer tested separately; the previous behavior broke newer pathlib features if pathlib2 was installed (see #592)

Fixes

  • correctly handle byte paths in os.path.exists (see #595)
  • Update fake_pathlib to support changes coming in Python 3.10 (see
  • correctly handle UNC paths in os.path.split and in directory path evaluation (see #606)

Infrastructure

  • added mypy checks in CI (see #599)

Version 4.4.0 (2021-02-24)

Adds better support for Python 3.8 / 3.9.

New Features

  • added support for pathlib.Path.link_to (new in Python 3.8) (see #580)
  • added support for pathlib.Path.readlink (new in Python 3.9) (see #584)
  • added FakeFilesystem.create_link convenience method which creates intermittent directories (see #580)

Fixes

  • fixed handling of pipe descriptors in the fake filesystem (see #581)
  • added non-functional argument effective_ids to os.access (see #585)
  • correctly handle os.file for unreadable files (see #588)

Infrastructure

  • added automatic documentation build and check-in

Version 4.3.3 (2020-12-20)

Another bugfix release.

Fixes

  • Reverted one Windows-specific optimization that can break tests under some conditions (see #573)
  • Setting os did not reset os.sep and related variables, fixed null device name, added os.pathsep and missing os.path variables (see #572)

Version 4.3.2 (2020-11-26)

This is a bugfix release that fixes a regression introduced in version 4.2.0.

Fixes

  • open calls had not been patched for modules with a name ending with “io” (see #569)

Version 4.3.1 (2020-11-23)

This is an update to the performance release, with more setup caching and the possibility to disable it.

Changes

  • Added caching of patched modules to avoid lookup overhead
  • Added use_cache option and clear_cache method to be able to deal with unwanted side effects of the newly introduced caching

Infrastructure

  • Moved CI builds to GitHub Actions for performance reasons

Version 4.3.0 (2020-11-19)

This is mostly a performance release. The performance of the pyfakefs setup has been decreasing sufficiently, especially with the 4.x releases. This release corrects that by making the most expansive feature optional, and by adding some other performance improvements. This shall decrease the setup time by about a factor of 20, and it shall now be comparable to the performance of the 3.4 release.

Changes

  • The patchfs decorator now expects a positional argument instead of the keyword arguments fs. This avoids confusion with the pytest fs fixture and conforms to the behavior of mock.patch. You may have to adapt the argument order if you use the patchfs and mock.patch decorators together (see #566)
  • Default arguments that are file system functions are now not patched by default to avoid a large performance impact. An additional parameter patch_default_args has been added that switches this behavior on (see #567).
  • Added performance improvements in the test setup, including caching the the unpatched modules

Version 4.2.1 (2020-11-02)

This is a bugfix release that fixes a regression issue.

Fixes

  • remove dependency of pyfakefs on pytest (regression, see #565)

Version 4.2.0 (2020-11-01)

New Features

  • add support for the buffering parameter in open (see #549)
  • add possibility to patch io.open_code using the new argument patch_open_code (since Python 3.8) (see #554)
  • add possibility to set file system OS via FakeFilesystem.os

Fixes

  • fix check for link in os.walk (see #559)
  • fix handling of real files in combination with home if simulating Posix under Windows (see #558)
  • do not call fake open if called from skipped module
    (see #552)
  • do not call fake pathlib.Path if called from skipped module
    (see #553)
  • fixed handling of additional_skip_names with several module components
  • allow to open existing pipe file descriptor (see #493)
  • do not truncate file on failed flush (see #548)
  • suppress deprecation warnings while collecting modules (see #542)
  • add support for os.truncate and os.ftruncate (see #545)

Infrastructure

  • fixed another problem with CI test scripts not always propagating errors
  • make sure pytest will work without pyfakefs installed (see #550)

Version 4.1.0 (2020-07-12)

New Features

  • Added some support for pandas (read_csv, read_excel and more), and for django file locks to work with the fake filesystem (see #531)

Fixes

  • os.expanduser now works with a bytes path
  • Do not override global warnings setting in Deprecator (see #526)
  • Make sure filesystem modules in pathlib are patched (see #527)
  • Make sure that alternative path separators are correctly handled under Windows (see #530)

Infrastructure

  • Make sure all temporary files from real fs tests are removed

Version 4.0.2 (2020-03-04)

This as a patch release that only builds for Python 3. Note that versions 4.0.0 and 4.0.1 will be removed from PyPi to disable installing them under Python 2.

Fixes

  • Do not build for Python 2 (see #524)

Version 4.0.1 (2020-03-03)

This as a bug fix release for a regression bug.

Note: This version has been yanked from PyPi as it erroneously allowed installation under Python 2. This has been fixed in version 4.0.2.

Fixes

  • Avoid exception if using flask-restx (see #523)

Version 4.0.0 (2020-03-03)

pyfakefs 4.0.0 drops support for Python 2.7. If you still need Python 2.7, you can continue to use pyfakefs 3.7.x.

Note: This version has been yanked from PyPi as it erroneously allowed installation under Python 2. This has been fixed in version 4.0.2.

Changes

  • Removed Python 2.7 and 3.4 support (see #492)

New Features

  • Added support for handling keyword-only arguments in some os functions
  • Added possibility to pass additional parameters to fs pytest fixture
  • Added automatic patching of default arguments that are file system functions
  • Added convenience decorator patchfs to patch single functions using the fake filesystem

Fixes

  • Added missing st_ino in makedir (see #515)
  • Fixed handling of relative paths in lresolve / os.lstat (see #516)
  • Fixed handling of byte string paths (see #517)
  • Fixed os.walk if path ends with path separator (see #512)
  • Fixed handling of empty path in os.makedirs (see #510)
  • Fixed handling of os.TMPFILE flag under Linux (see #509 and #511)
  • Adapted fake pathlib to changes in Python 3.7.6/3.8.1
    (see #508)
  • Fixed behavior of os.makedirs in write-protected directory (see #507)

Version 3.7.2 (2020-03-02)

This version backports some fixes from master.

Fixes

  • Fixed handling of relative paths in lresolve / os.lstat (see #516)
  • Fixed os.walk if path ends with path separator (see #512)
  • Fixed handling of empty path in os.makedirs (see #510)
  • Fixed handling of os.TMPFILE flag under Linux (see #509 and #511)
  • Fixed behavior of os.makedirs in write-protected directory (see #507)

Version 3.7.1 (2020-02-14)

This version adds support for Python 3.7.6 and 3.8.1.

Fixes

  • Adapted fake pathlib to changes in Python 3.7.6/3.8.1
    (see #508) (backported from master)

Version 3.7 (2019-11-23)

This version adds support for Python 3.8.

Note: This is the last pyfakefs version that will support Python 2.7 and Python 3.4 (possible bug fix releases notwithstanding).

New Features

  • added support for Python 3.8 (see #504)
  • added preliminary support for Windows-specific os.stat_result attributes tst_file_attributes and st_reparse_tag (see #504)
  • added support for fake os.sendfile (Posix only, Python 3 only) (see #504)

Fixes

  • support devnull in Windows under Python 3.8 (see #504)
  • fixed side effect of calling DirEntry.stat() under Windows (changed st_nlink) (see #502)
  • fixed problem of fake modules still referenced after a test in modules loaded during the test (see #501 and #427)
  • correctly handle missing read permission for parent directory (see #496)
  • raise for os.scandir with non-existing directory (see #498)

Infrastructure

  • fixed CI tests scripts to always propagate errors (see #500)

Version 3.6.1 (2019-10-07)

Fixes

  • avoid rare side effect during module iteration in test setup (see #338)
  • make sure real OS tests are not executed by default (see #495)

Version 3.6 (2019-06-30)

Changes

  • removed unneeded parameter use_dynamic_patch

New Features

  • support for src_dir_fd and dst_dir_fd arguments in os.rename, os.replace and os.link
  • added possibility to use modules instead of module names for the additional_skip_names argument (see #482)
  • added argument allow_root_user to Patcher and UnitTest to allow forcing non-root access (see #474)
  • added basic support for os.pipe (see #473)
  • added support for symlinks in add_real_directory
  • added new public method add_real_symlink

Infrastructure

  • added check for correctly installed Python 3 version in Travis.CI (see #487)

Fixes

  • fixed incorrect argument names for some os functions
  • fake DirEntry now implements os.PathLike in Python >= 3.6 (see #483)
  • fixed incorrect argument name for os.makedirs (see #481)
  • avoid pytest warning under Python 2.7 (see #466)
  • add next to FakeFileWrapper (see #485)

Version 3.5.8 (2019-06-21)

Another bug-fix release that mainly fixes a regression wih Python 2 that has been introduced in version 3.5.3.

Fixes

  • regression: patching build-in open under Python 2 broke unit tests (see #469)
  • fixed writing to file added with add_real_file (see #470)
  • fixed argument name of FakeIOModule.open (see #471)

Infrastructure

  • more changes to run tests using python setup.py test under Python 2 regardless of pathlib2 presence

Version 3.5.7 (2019-02-08)

This is mostly a bug-fix release.

Fixes

  • regression: pathlib did not get patched in the presence of pathlib2 (see #467)
  • fixed errors if running the PyCharm debugger under Python 2 (see #464)

Infrastructure

  • do not run real file system tests by default (fixes deployment problem, see #465)
  • make tests run if running python setup.py test under Python 2

Version 3.5.6 (2019-01-13)

Changes

  • import external pathlib2 and scandir packages first if present (see #462)

Version 3.5.5 (2018-12-20)

Fixes

  • removed shebang from test files to avoid packaging warnings (see #461)

Version 3.5.4 (2018-12-19)

New Features

  • added context manager class Pause for pause/resume (see #448)

Fixes

  • fixed AttributeError shown while displaying fs in a failing pytest in Python 2
  • fixed permission handling for root user
  • avoid AttributeError triggered by modules without __module__ attribute (see #460)

Version 3.5.3 (2018-11-22)

This is a minor release to have a version with passing tests for OpenSUSE packaging.

New Features

  • automatically patch file system methods imported as another name like from os.path import exists as my_exists, including builtin open and io.open

Fixes

  • make tests for access time less strict to account for file systems that do not change it immediately (#453)

Version 3.5.2 (2018-11-11)

This is mostly a bug-fix release.

New Features

  • added support for pause/resume of patching the file system modules (#448)
  • allow to set current group ID, set current user ID and group ID as st_uid and st_gid in new files (#449)

Fixes

  • fixed using modules_to_patch (regression, see #450)
  • fixed recursion error on unpickling the fake file system (#445)
  • allow trailing path in add_real_directory (#446)

Version 3.5 (2018-10-22)

Changes

  • This version of pyfakefs does not support Python 3.3. Python 3.3 users must keep using pyfakefs 3.4.3, or upgrade to a newer Python version.
  • The deprecation warnings for the old API are now switched on by default. To switch them off for legacy code, use:
    from pyfakefs.deprecator import Deprecator
    Deprecator.show_warnings = False
    

New Features

  • Improved automatic patching:
    • automatically patch methods of a patched file system module imported like from os.path import exists (#443)
    • a module imported as another name (import os as _os) is now correctly patched without the need of additional parameters (#434)
    • automatically patch Path if imported like from pathlib import Path (#440)
    • parameter patch_path has been removed from UnitTest and Patcher, the correct patching of path imports is now done automatically (#429)
    • UnitTest /Patcher arguments can now also be set in setUpPyfakefs() (#430)
  • added possibility to set user ID (#431)
  • added side_effect option to fake files (#433)
  • added some support for extended filesystem attributes under Linux (#423)
  • handle contents=None in create_file() as empty contents if size not set (#424)
  • added pathlib2 support (#408) (#422)
  • added support for null device (#418)
  • improved error message for “Bad file descriptor in fake filesystem” (#419)

Fixes

  • fixed pytest when both pyfakefs and future are installed (#441)
  • file timestamps are now updated more according to the real behavior (#435)
  • fixed a problem related to patching shutil functions using zipfile (#427)

Version 3.4.3 (2018-06-13)

This is mostly a bug fix release, mainly for bugs found by @agroce using tstl.

New Features

  • added support for path-like objects as arguments in create_file(), create_dir(), create_symlink(), add_real_file() and add_real_directory() (Python >= 3.6, see #409)

Infrastructure

  • moved tests into package
  • use README.md in pypi (#358)

Fixes

  • tell after seek gave incorrect result in append mode (#363)
  • a failing pytest did not display the test function correctly (#381)
  • flushing file contents after truncate was incorrect under some conditions (#412)
  • readline() did not work correctly in binary mode (#411)
  • pathlib.Path.resolve() behaved incorrectly if the path does not exist (#401)
  • closed attribute was not implemented in fake file (#380)
  • add_real_directory did not behave correctly for nested paths
  • the following functions did not behave correctly for paths ending with a path separator (found by @agroce using tstl):

Version 3.4.1 (2018-03-18)

This is a bug fix only release.

Fixes

  • Missing cleanup after using dynamic patcher let to incorrect behavior of tempfile after test execution (regression, see #356)
  • add_real_directory does not work after chdir (see #355)

Version 3.4 (2018-03-08)

This version of pyfakefs does not support Python 2.6. Python 2.6 users must use pyfakefs 3.3 or earlier.

New Features

  • Added possibility to map real files or directories to another path in the fake file system (see #347)
  • Configuration of Patcher and TestCase:
    • Possibility to reload modules is now also available in Patcher
    • Added possibility to add own fake modules via modules_to_patch argument (see #345)
    • Dynamic loading of modules after setup is now on by default and no more considered experimental (see #340)
  • Added support for file descriptor path parameter in os.scandir (Python >= 3.7, Posix only) (see #346)
  • Added support to fake out backported scandir module (#332)
  • IOError/OSError exception messages in the fake file system now always start with the message issued in the real file system in Unix systems (see #202)

Infrastructure

  • Changed API to be PEP-8 conform (#186). Note: The old API is still available.
  • Removed Python 2.6 support (#293)
  • Added usage documentation to GitHub Pages
  • Added contributing guide
  • Added flake8 tests to Travis CI

Fixes

  • Links in base path in os.scandir shall not be resolved (#350)
  • Fixed unit tests when run on a computer not having umask set to 0022
  • Correctly handle newline parameter in open() for Python 3, added support for universal newline mode in Python 2 (#339)
  • Fixed handling of case-changing rename with symlink under MacOS (#322)
  • Creating a file with a path ending with path separator did not raise (#320)
  • Fixed more problems related to flush (#302, #300)
  • Correctly handle opening files more than once (#343)
  • Fake os.lstat() crashed with several trailing path separators (#342)
  • Fixed handling of path components starting with a drive letter(#337)
  • Symlinks to absolute paths were incorrectly resolved under Windows (#341)
  • Unittest mock didn't work after setUpPyfakefs (#334)
  • os.path.split() and os.path.dirname() gave incorrect results under Windows (#335)

Version 3.3 (2017-11-12)

This is the last release that supports Python 2.6.

New Features

  • The OS specific temp directory is now automatically created in setUp() (related to #191). Note that this may break test code that assumes that the fake file system is completely empty at test start.
  • Added possibility to reload modules and switch on dynamic loading of modules after setup (experimental, see #248)
  • Added possibility to patch modules that import file system modules under another name, for example import os as '_os (#231)
  • Added support for dir_fd argument in several os functions (#206)
  • Added support for open file descriptor as path argument in os.utime, os.chmod, os.chdir, os.chown, os.listdir, os.stat and os.lstat (Python >= 3.3) (#205)
  • Added support for basic modes in fake os.open() (#204)
  • Added fake os.path.samefile implementation (#193)
  • Added support for ns argument in os.utime() (Python >= 3.3) (#192)
  • Added nanosecond time members in os.stat_result (Python >= 3.3) (#196)

Infrastructure

  • Added Travis CI tests for MacOSX (Python 2.7 and 3.6)
  • Added Appveyor CI tests for Windows (Python 2.7, 3.3 and 3.6)
  • Added auto-generated documentation for development version on GitHub Pages
  • Removed most of fake_filesystem_shutil implementation, relying on the patched os module instead (#194)
  • Removed fake_tempfile and fake_filesystem_glob, relying on the patched os module instead (#189, #191)

Fixes

  • Multiple fixes of bugs found using TSTL by @agroce (see about 100 issues with the TSTL label)
    • several problems with buffer handling in high-level IO functions
    • several problems with multiple handles on the same file
    • several problems with low-level IO functions
    • incorrect exception (IOError vs OSError) raised in several cases
    • Fake rename did not behave like os.rename in many cases
    • Symlinks have not been considered or incorrectly handled in several functions
    • A nonexistent file that has the same name as the content of the parent object was seen as existing
    • Incorrect error handling during directory creation
    • many fixes for OS-specific behavior
  • Also patch modules that are loaded between __init__() and setUp() (#199)
  • Creating files in read-only directory was possible (#203)

Version 3.2 (2017-05-27)

New Features

  • The errors argument is supported for io.open() and os.open()
  • New methods add_real_file(), add_real_directory() and add_real_paths() make real files and directories appear within the fake file system. File contents are read from the real file system only as needed (#170). See example_test.py for a usage example.
  • Deprecated TestCase.copyRealFile() in favor of add_real_file(). copyRealFile() remains only for backward compatability. Also, some less-popular argument combinations have been disallowed.
  • Added this file you are reading, CHANGES.md, to the release manifest

Infrastructure

  • The mox3 package is no longer a prerequisite--the portion required by pyfakefs has been integrated into pyfakefs (#182)

Fixes

  • Corrected the handling of byte/unicode paths in several functions (#187)
  • FakeShutilModule.rmtree() failed for directories ending with path separator (#177)
  • Case was incorrectly handled for added Windows drives
  • pathlib.glob() incorrectly handled case under MacOS (#167)
  • tox support was broken (#163)
  • On Windows it was not possible to rename a file when only the case of the file name changed (#160)

Version 3.1 (2017-02-11)

New Features

  • Added helper method TestCase.copyRealFile() to copy a file from the real file system to the fake file system. This makes it easy to use template, data and configuration files in your tests.
  • A pytest plugin is now installed with pyfakefs that exports the fake filesystem as pytest fixture fs.

Fixes

  • Incorrect disk usage calculation if too large file created (#155)

Version 3.0 (2017-01-18)

New Features

  • Support for path-like objects as arguments in fake os and os.path modules (Python >= 3.6)
  • Some changes to make pyfakefs work with Python 3.6
  • Added fake pathlib module (Python >= 3.4) (#29)
  • Support for os.replace (Python >= 3.3)
  • os.access, os.chmod, os.chown, os.stat, os.utime: support for follow_symlinks argument (Python >= 3.3)
  • Support for os.scandir (Python >= 3.5) (#119)
  • Option to not fake modules named path (#53)
  • glob.glob, glob.iglob: support for recursive argument (Python >= 3.5) (#116)
  • Support for glob.iglob (#59)

Infrastructure

Fixes

  • shutil.move incorrectly moves directories (#145)
  • Missing support for ‘x’ mode in open (Python >= 3.3) (#147)
  • Incorrect exception type in Posix if path ancestor is a file (#139)
  • Exception handling when using Patcher with py.test (#135)
  • Fake os.listdir returned sorted instead of unsorted entries

Version 2.9 (2016-10-02)

New Features

  • io.open, os.open: support for encoding argument (#120)
  • os.makedirs: support for exist_ok argument (Python >= 3.2) (#98)
  • Support for fake io.open() (#70)
  • Support for mount points (#25)
  • Support for hard links (#75)
  • Support for float times (mtime, ctime)
  • Windows support:
    • support for alternative path separator
    • support for case-insensitive filesystems (#69)
    • support for drive letters and UNC paths
  • Support for filesystem size (#86)
  • shutil.rmtree: support for ignore_errors and onerror arguments (#72)
  • Support for os.fsync() and os.fdatasync() (#73)
  • os.walk: Support for followlinks argument

Fixes

  • shutil functions like make_archive do not work with pyfakefs (#104)
  • File permissions on deletion not correctly handled (#27)
  • shutil.copy error with bytes contents (#105)
  • mtime and ctime not updated on content changes

Version 2.7

Infrastructure

  • Moved repository from GoogleCode to GitHub, merging 3 projects
  • Added continuous integration testing with Travis CI
  • Added usage documentation in project wiki
  • Better support for pypi releases

New Features

  • Added direct unit test support in fake_filesystem_unittest (transparently patches all calls to faked implementations)
  • Added support for doctests
  • Added support for cygwin
  • Better support for Python 3

Fixes

  • os.utime fails to traverse symlinks (#49)
  • chown incorrectly accepts non-integer uid/gid arguments (#30)
  • Reading from fake block devices doesn't work (#24)
  • fake_tempfile is using AddOpenFile incorrectly (#23)
  • Incorrect behavior of relpath, abspath and normpath on Windows.
  • Cygwin wasn't treated as Windows (#37)
  • Python 3 open in binary mode not working (#32)
  • os.remove doesn't work with relative paths (#31)
  • mkstemp returns no valid file descriptor (#19)
  • open methods lack IOError for prohibited operations (#18)
  • Incorrectly resolved relative path (#3)
  • FakeFileOpen keyword args do not match the __builtin__ equivalents (#5)
  • Relative paths not supported (#16, #17))

Older Versions

There are no release notes for releases 2.6 and below. The following versions are still available on PyPi: