PyYAML

PyYAML is a YAML parser and emitter for Python.

Overview

YAML is a data serialization format designed for human readability and interaction with scripting languages.

PyYAML is a YAML parser and emitter for the Python programming language.

PyYAML features

a complete YAML 1.1 parser. In particular, PyYAML can parse all examples from the specification. The parsing algorithm is simple enough to be a reference for YAML parser implementors.
Unicode support including UTF-8/UTF-16 input/output and *
low-level event-based parser and emitter API (like SAX).
high-level API for serializing and deserializing native Python objects (like DOM or pickle).
support for all types from the YAML types repository. A simple extension API is provided.
both pure-Python and fast LibYAML-based parsers and emitters.
relatively sensible error messages.

Requirements

PyYAML requires Python 2.7 or Python 3.5+.

Download and Installation

The current stable release of PyYAML: 5.3.

Download links:

TAR.GZ package: http://pyyaml.org/download/pyyaml/PyYAML-5.3.1.tar.gz
Windows installers (32-bit):
- http://pyyaml.org/download/pyyaml/PyYAML-5.3.1-cp27-cp27m-win32.whl (for Python 2.7)
- http://pyyaml.org/download/pyyaml/PyYAML-5.3.1-cp35-cp35m-win32.whl (for Python 3.5)
- http://pyyaml.org/download/pyyaml/PyYAML-5.3.1-cp36-cp36m-win32.whl (for Python 3.6)
- http://pyyaml.org/download/pyyaml/PyYAML-5.3.1-cp37-cp37m-win32.whl (for Python 3.7)
- http://pyyaml.org/download/pyyaml/PyYAML-5.3.1-cp38-cp38m-win32.whl (for Python 3.8)
Windows installers (64-bit):
- http://pyyaml.org/download/pyyaml/PyYAML-5.3.1-cp27-cp27m-win_amd64.whl (for Python 2.7)
- http://pyyaml.org/download/pyyaml/PyYAML-5.3.1-cp35-cp35m-win_amd64.whl (for Python 3.5)
- http://pyyaml.org/download/pyyaml/PyYAML-5.3.1-cp36-cp36m-win_amd64.whl (for Python 3.6)
- http://pyyaml.org/download/pyyaml/PyYAML-5.3.1-cp37-cp37m-win_amd64.whl (for Python 3.7)
- http://pyyaml.org/download/pyyaml/PyYAML-5.3.1-cp38-cp38m-win_amd64.whl (for Python 3.8)

Unpack the archive and install the package by executing

$ python setup.py install

If you want to use LibYAML bindings, you need to download and install LibYAML. Then you may install the bindings by executing

$ python setup.py --with-libyaml install

The source distribution includes a comprehensive test suite. To run the tests, type

$ python setup.py test

Documentation

Quick example (see documentation for loading multiple documents):

>>> import yaml

>>> print yaml.load("""
... name: Vorlin Laruknuzum
... sex: Male
... class: Priest
... title: Acolyte
... hp: [32, 71]
... sp: [1, 13]
... gold: 423
... inventory:
... - a Holy Book of Prayers (Words of Wisdom)
... - an Azure Potion of Cure Light Wounds
... - a Silver Wand of Wonder
... """)

{'name': 'Vorlin Laruknuzum', 'gold': 423, 'title': 'Acolyte', 'hp': [32, 71],
'sp': [1, 13], 'sex': 'Male', 'inventory': ['a Holy Book of Prayers (Words of Wisdom)',
'an Azure Potion of Cure Light Wounds', 'a Siver Wand of Wonder'], 'class': 'Priest'}

>>> print yaml.dump({'name': "The Cloak 'Colluin'", 'depth': 5, 'rarity': 45,
... 'weight': 10, 'cost': 50000, 'flags': ['INT', 'WIS', 'SPEED', 'STEALTH']})

name: The Cloak 'Colluin'
rarity: 45
flags: [INT, WIS, SPEED, STEALTH]
weight: 10
cost: 50000
depth: 5

For more details, please check PyYAML Documentation.

History

5.3.1 (2020-03-18)

#386 – Prevents arbitrary code execution during python/object/new constructor

5.3 (2020-01-06)

#290 – Use is instead of equality for comparing with None
#270 – fix typos and stylistic nit
#309 – Fix up small typo
#161 – Fix handling of slots
#358 – Allow calling add_multi_constructor with None
#285 – Add use of safe_load() function in README
#351 – Fix reader for Unicode code points over 0xFFFF
#360 – Enable certain unicode tests when maxunicode not > 0xffff
#359 – Use full_load in yaml-highlight example
#244 – Document that PyYAML is implemented with Cython
#329 – Fix for Python 3.10
#310 – increase size of index, line, and column fields
#260 – remove some unused imports
#163 – Create timezone-aware datetimes when parsed as such
#363 – Add tests for timezone

5.2 (2019-12-02)

Repair incompatibilities introduced with 5.1. The default Loader was changed, but several methods like add_constructor still used the old default #279 – A more flexible fix for custom tag constructors #287 – Change default loader for yaml.add_constructor #305 – Change default loader for add_implicit_resolver, add_path_resolver
Make FullLoader safer by removing python/object/apply from the default FullLoader #347 – Move constructor for object/apply to UnsafeConstructor
Fix bug introduced in 5.1 where quoting went wrong on systems with sys.maxunicode <= 0xffff #276 – Fix logic for quoting special characters
Other PRs: #280 – Update CHANGES for 5.1

5.1 (2019-03-13)

Incompatible changes:
#257 – Deprecate yaml.load and add FullLoader and UnsafeLoader classes
#256 – Make default_flow_style=False
Features:
#158 – Support escaped slash in double quotes “/”
#45 – Allow colon in a plain scalar in a flow context
#63 – Adding support to Unicode characters over codepoint 0xffff
#254 – Allow to turn off sorting keys in Dumper
Bugfixes:
#129 – Remove call to ord in lib3 emitter code
Other:
#35 – Some modernization of the test running
#42 – Install tox in a virtualenv
#48 – Fix typos
#55 – Improve RepresenterError creation
#59 – Resolves #57, update readme issues link
#60 – Document and test Python 3.6 support
#61 – Use Travis CI built in pip cache support
#62 – Remove tox workaround for Travis CI
#75 – add 3.12 changelog
#76 – Fallback to Pure Python if Compilation fails
#84 – Drop unsupported Python 3.3
#102 – Include license file in the generated wheel package
#105 – Removed Python 2.6 & 3.3 support
#111 – Remove commented out Psyco code
#149 – Test on Python 3.7-dev
#175 – Updated link to pypi in release announcement
#181 – Import Hashable from collections.abc
#194 – Reverting https://github.com/yaml/pyyaml/pull/74
#195 – Build libyaml on travis
#196 – Force cython when building sdist
#261 – Skip certain unicode tests when maxunicode not > 0xffff
#263 – Windows Appveyor build

3.13 (2018-07-05)

Rebuild wheels using latest Cython for Python 3.7 support.

3.12 (2016-08-28)

Wheel packages for Windows binaries.
Adding an implicit resolver to a derived loader should not affect the base loader (fixes issue #57).
Uniform representation for OrderedDict across different versions of Python (fixes issue #61).
Fixed comparison to None warning (closes issue #64).

3.11 (2014-03-26)

Source and binary distributions are rebuilt against the latest versions of Cython and LibYAML.

3.10 (2011-05-30)

Do not try to build LibYAML bindings on platforms other than CPython; this fixed installation under Jython (Thank to olt(at)bogosoft(dot)com).
Clear cyclic references in the parser and the emitter (Thank to kristjan(at)ccpgames(dot)com).
LibYAML bindings are rebuilt with the latest version of Cython.
Dropped support for Python 2.3 and 2.4; currently supported versions are 2.5 to 3.2.

3.09 (2009-08-31)

Fixed use of uninitialized memory when emitting anchors with LibYAML bindings (Thank to cegner(at)yahoo-inc(dot)com).
Fixed emitting incorrect BOM characters for UTF-16 (Thank to Valentin Nechayev)
Fixed the emitter for folded scalars not respecting the preferred line width (Thank to Ingy).
Fixed a subtle ordering issue with emitting %TAG directives (Thank to Andrey Somov).
Fixed performance regression with LibYAML bindings.

3.08 (2008-12-31)

Python 3 support (Thank to Erick Tryzelaar).
Use Cython instead of Pyrex to build LibYAML bindings.
Refactored support for unicode and byte input/output streams.

3.07 (2008-12-29)

The emitter learned to use an optional indentation indicator for block scalar; thus scalars with leading whitespaces could now be represented in a literal or folded style.
The test suite is now included in the source distribution. To run the tests, type python setup.py test.
Refactored the test suite: dropped unittest in favor of a custom test appliance.
Fixed the path resolver in CDumper.
Forced an explicit document end indicator when there is a possibility of parsing ambiguity.
More setup.py improvements: the package should be usable when any combination of setuptools, Pyrex and LibYAML is installed.
Windows binary packages are built against LibYAML-0.1.2.
Minor typos and corrections. Thank to Ingy dot Net and Andrey Somov.

3.06 (2008-10-03)

setup.py checks whether LibYAML is installed and if so, builds and installs LibYAML bindings. To force or disable installation of LibYAML bindings, use --with-libyaml or --without-libyaml respectively (partially fixes #34).
Building LibYAML bindings no longer requires Pyrex installed (fixed #33).
yaml.load() raises an exception if the input stream contains more than one YAML document (fixed #54).
Fixed exceptions produced by LibYAML bindings (fixed #50).
Fixed a dot '.' character being recognized as !!float (fixed #62).
Fixed Python 2.3 compatibility issue in constructing !!timestamp values.
Windows binary packages are built against the LibYAML stable branch.
Added attributes yaml.__version__ and yaml.__with_libyaml__ (fixed #85).

3.05 (2007-05-13)

Allow for immutable subclasses of YAMLObject. Fixed #53.
Make the encoding of the unicode->str conversion explicit; fixed #52.
Fixed a problem when the DOCUMENT-END event is not emitted until the beginning of the next document is available. Fixed #51. Thanks edward(at)sweetbytes.net for the bug report.
Improve output of float values. Fixed #49.
Fix the bug when the path in add_path_resolver contains boolean values. Fixed #43 (thanks to jstroud(at)mbi.ucla.edu for reporting and pointing to the cause).
Use the types module instead of constructing type objects by hand. Fixed #41. Thanks to v.haisman(at)sh.cvut.cz for the patch.
Fix loss of microsecond precision in datetime.datetime constructor (fix #30). Thanks to edemaine(at)mit.edu for the bug report and the patch.
Fixed loading an empty YAML stream.

3.04 (2006-08-20)

Include experimental LibYAML bindings.
Fully support recursive structures (close #5).
Sort dictionary keys (close #23). Mapping node values are now represented as lists of pairs instead of dictionaries. Do not check for duplicate mapping keys as it didn’t work correctly anyway.
Fix invalid output of single-quoted scalars in cases when a single quote is not escaped when preceeded by whitespaces or line breaks (close #17).
To make porting easier, rewrite Parser not using generators.
Fix handling of unexpected block mapping values, like {{{ : foo }}}
Fix a bug in Representer.represent_object: copy_reg.dispatch_table was not correctly handled.
Fix a bug when a block scalar is incorrectly emitted in the simple key context.
Hold references to the objects being represented (close #22).
Make Representer not try to guess !!pairs when a list is represented.
Fix timestamp constructing and representing (close #25).
Fix the ‘N’ plain scalar being incorrectly recognized as !!bool (close #26).

3.03 (2006-06-19)

Fix Python 2.5 compatibility issues.
Fix numerous bugs in the float handling.
Fix scanning some ill-formed documents.
Other minor fixes.

3.02 (2006-05-15)

Fix win32 installer. Apparently bdist_wininst does not work well under Linux.
Fix a bug in add_path_resolver.
Add the yaml-highlight example. Try to run on a color terminal: python yaml_hl.py <any_document.yaml.

3.01 (2006-05-07)

Initial release. The version number reflects the codename of the project (PyYAML 3000) and differenciates it from the abandoned PyYaml module.

Author and Copyright

The PyYAML module was written by Kirill Simonov. It is now maintained by the YAML community.

PyYAML is released under the MIT license.