by Christoph Gohlke, Laboratory for Fluorescence Dynamics, University of California, Irvine.
Updated on 19 January 2022 at 04:27 UTC.
This page provides 32 and 64-bit Windows binaries of many scientific open-source extension packages for the official CPython distribution of the Python programming language. A few binaries are available for the PyPy distribution.
The files are unofficial (meaning: informal, unrecognized, personal, unsupported, no warranty, no liability, provided "as is") and made available for testing and evaluation purposes.
Most binaries are built from source code found on PyPI or in the projects public revision control systems. Source code changes, if any, have been submitted to the project maintainers or are included in the packages.
Refer to the documentation of the individual packages for license restrictions and dependencies.
If downloads fail, reload this page, enable JavaScript, disable download managers, disable proxies, clear cache, use Firefox, reduce number and frequency of downloads. Please only download files manually as needed.
Use pip version 19.2 or newer to install the downloaded .whl files. This page is not a pip package index.
Many binaries depend on numpy+mkl and the current Microsoft Visual C++ Redistributable for Visual Studio 2015-2022 for Python 3, or the Microsoft Visual C++ 2008 Redistributable Package x64, x86, and SP1 for Python 2.7.
Install numpy+mkl before other packages that depend on it.
The binaries are compatible with the most recent official CPython distributions on Windows >=6.0. Chances are they do not work with custom Python distributions included with Blender, Maya, ArcGIS, OSGeo4W, ABAQUS, Cygwin, Pythonxy, Canopy, EPD, Anaconda, WinPython etc. Many binaries are not compatible with Windows XP, Windows 7, or Wine.
The packages are ZIP or 7z files, which allows for manual or scripted installation or repackaging of the content.
The files are provided "as is" without warranty or support of any kind. The entire risk as to the quality and performance is with you.
The opinions or statements expressed on this page should not be taken as a position or endorsement of the Laboratory for Fluorescence Dynamics or the University of California.
- Index by date:
- pytomlpp
- pyopencl
- regex
- scs
- frozenlist
- edt
- jupyter
- pymor
- psdtags
- pyturbojpeg
- igraph
- swiglpk
- fabio
- pyrsistent
- cartopy
- numba
- llvmlite
- dulwich
- pymatgen
- iminuit
- scikits.odes
- ta-lib
- fonttools
- arctic
- imagecodecs
- apsw
- jellyfish
- orange
- gmpy
- ecos
- recordclass
- mercurial
- bitarray
- fiona
- rasterio
- gdal
- ruamel.yaml
- pillow-simd
- zstd
- pygame
- kwant
- osqp
- kivy
- pandas
- pygeos
- basemap
- opencv
- pillow
- pytables
- maturin
- pylibjpeg
- pyproj
- triangle
- qdldl
- pyfmi
- assimulo
- numpy
- cantera
- sounddevice
- pydantic
- h5py
- netcdf4
- pyaudio
- shapely
- guiqwt
- line_profiler
- pyrxp
- reportlab
- glymur
- matplotlib
- cupy
- cvxopt
- cvxpy
- py-lmdb
- psycopg
- psutil
- pycuda
- pyslalib
- pymc
- slycot
- pyspharm
- tomopy
- qutip
- scipy
- liblinear
- mkl-service
- mkl_fft
- mkl_random
- numexpr
- pycryptosat
- boost.python
- cx_freeze
- cx_logging
- scikit-learn
- pyamg
- pymssql
- pyzstd
- ujson
- sqlalchemy
- dtaidistance
- pytoshop
- pywin32
- louvain-igraph
- glfw
- discretize
- pyephem
- coverage
- pymol-open-source
- cython
- jcc
- tinyarray
- lazy_object_proxy
- scikit-image
- lsqfit
- gvar
- cmarkgfm
- lxml
- pygit2
- gevent
- spacy
- pymongo
- spglib
- pyheif
- typed_ast
- orjson
- mistune
- xgboost
- pyicu
- caterva
- python-ldap
- lz4
- aicspylibczi
- bfloat16
- mpi4py
- msgpack
- vispy
- sasl
- atom
- fastparquet
- autobahn
- enaml
- bottleneck
- sdtfile
- simplejson
- pywinpty
- aiohttp
- fast-histogram
- moderngl
- boost-histogram
- aggdraw
- btrees
- fastcluster
- glumpy
- google-crc32c
- pyhdf
- protobuf
- udunits
- scikits.vectorplot
- scandir
- wordcloud
- biopython
- openexr
- pillow-avif-plugin
- imread
- traits
- pycares
- freetypepy
- msvc_runtime
- statsmodels
- mahotas
- fastrlock
- pyjnius
- cftime
- numpy-quaternion
- pylibtiff
- pyopengl
- mplcairo
- pycosat
- pycifrw
- rtree
- setproctitle
- pywavelets
- twainmodule
- videocapture
- vidsrc
- transformations
- akima
- psf
- lfdfiles
- chebyfit
- python-lzf
- numcodecs
- bitshuffle
- rapidjson
- indexed_gzip
- pycurl
- pyzmq
- twisted
- pycairo
- cairocffi
- blosc
- pyyaml
- zopflipy
- python-snappy
- brotli
- cffi
- kiwisolver
- fastremap
- mayavi
- vtk
- imgui
- thinc
- cytoolz
- cx_oracle
- pyerfa
- psygnal
- cramjam
- jpegio
- yarl
- tifffile
- lightgbm
- opentsne
- wrapt
- hyperspy
- peewee
- texture2ddecoder
- debugpy
- blis
- cymem
- murmurhash
- srsly
- preshed
- partseg
- param
- gitdb
- leidenalg
- blosc2
- yappi
- multidict
- casa_formats_io
- zodbpickle
- greenlet
- thrift
- gensim
- iris
- openpiv
- numpy-stl
- openimageio
- icsdll
- liblas
- pyswisseph
- pystemmer
- pydde
- pykinsol
- pyhull
- pygresql
- pyemd
- pycvodes
- pycld2
- pybox2d
- py-earth
- polylearn
- planar
- pystruct
- pocketsphinx
- gpy
- enable
- scimath
- scikit-misc
- salientdetect
- pygraphviz
- curses
- stratify
- spectrum
- sima
- seqlearn
- heatmap
- hddm
- pyfltk
- libsvm
- cellprofiler
- medussa
- crcmod
- crc16
- sfepy
- datrie
- pylvgl
- fasttext
- sparsesvd
- simpleparse
- freesasa
- dukpy
- pycluster
- pycorrfit
- intbitset
- pydensecrf
- cvxcanon
- python-levenshtein
- lru_dict
- logbook
- kapteyn
- jsonobject
- pendulum
- openbabel
- ode
- obspy
- nlopt
- lp_solve
- fpzip
- pyodbc
- backports.zoneinfo
- astropy
- hdbscan
- blist
- bintrees
- aspell-python
- annoy
- ahds
- ad3
- dawg
- fann2
- bsddb3
- winrandom
- ffnet
- fdint
- flann
- fisher
- fisx
- zfec
- wrf_python
- pyminuit
- pymaxflow
- pyzopfli
- pyx
- pytinyexr
- pystackreg
- pymetis
- pywinhook
- python-geohash
- llist
- pytiff
- pycudadecon
- mod_wsgi
- marisa-trie
- tiledb
- yt
- mxnet
- hmmlearn
- ets
- cobra
- natgrid
- cf-units
- dnacurve
- zeroc-ice
- multiprocess
- lightning
- uciwebauth
- molmass
- chaco
- holopy
- elasticdeform
- centrosome
- pyodeint
- pymvpa
- pymcubes
- zfpy
- simpleaudio
- python-javabridge
- grpcio
- pythonmagick
- pyalembic
- fcsfiles
- qdafile
- lucam
- imreg
- oiffile
- netpbmfile
- roifile
- jpype
- pypmc
- celiagg
- naturalneighbor
- xxhash
- cheetah
- ceodbc
- noise
- pylzma
- python-lzo
- zope.interface
- tornado
- rtmidi-python
- pyasn
- persistent
- markupsafe
- netifaces
- ndimage
- mysqlclient
- dipy
- babel
- slideio
- bsdiff4
- bcolz
- tinybrain
- pyeda
- tatsu
- polygon
- fmkr
- cmapfile
- javabridge
- pnumpy
- pythonnet
- menpo
- nitime
- goertzel-fft
- libsbml
- quickfix
- open3d
- xylib-py
- daal4py
- cchardet
- minepy
- zipline
- pulp
- simpleitk
- pytorch
- zs
- milk
- mlpy
- postgresadapter
- scikit-cycling
- pyqpbo
- pgmagick
- hdf5plugin
- pyfm
- pyflux
- entropy
- cyrasterize
- dubins
- debug-information-files
- qimage2ndarray
- imagecodecs-lite
- cgohlke
- imaged11
- pyside
- pyvrml97
- pylibczi
- backports.lzma
- x86cpu
- cdecimal
- brotlipy
- fastcache
- czifile
- pyclearvolume
- cellcognition
- vigra
- re2
- meshpy
- scikit-fmm
- pyhook
- fasttsne
- rpy2
- freeimagedll
- chompack
- pysqlite
- tensorflow
- multineat
- pyfits
- grako
- cyordereddict
- qt_graph_helpers
- veusz
- pyqwt
- pyqt4
- trollius
- faulthandler
- thriftpy
- pyldap
- autopy
- jsonlib
- quantlib
- scikit-umfpack
- gr
- pyarrow
- python-cjson
- py_gd
- nipy
- libtfr
- mathutils
- pyfftw
- pyviennacl
- blz
- bigfloat
- cyassimp
- pymca
- friture
- pycogent
- blaze
- scikits.audiolab
- la
- bazaar
- dynd
- genshi
- python-sundials
- pyamf
- libxml-python
- pymcmc
- pyksvd
- pybluez
- mxbase
- libpython
- pymunk
- pygtk
- cgal-bindings
- bio_formats
- pysfml
- pyexiv2
- pylibdeconv
- iocbio
- pymix
- umysql
- lazyflow
- mmlib
- scikits.timeseries
- casuarius
- wxpython
- ilastik
- pywcs
- scientificpython
- vpython
- nmoldyn
- mmtk
- polymode
- scikits.delaunay
- cld
- py-fcm
- oursql
- py2exe
- pymutt
- carray
- llvmpy
- cgkit
- pymedia
- scipy-cluster
- scikits.scattpy
- scikits.samplerate
- scikits.ann
- pyxml
- pytst
- delny
- mysql-python
- htseq
- pyusb-ftdi
- silvercity
- steps
- pysparse
- pyropes
- scikits.hydroclimpy
- sendkeys
- pydbg
- pyisapie
-
- AD3: Alternating Directions Dual Decomposition.
- Aggdraw: a high-quality graphics engine for PIL based on the
Anti-Grain Geometry library.
- Ahds: access headers and data streams in Amira(R) files.
- Aicspylibczi: expose libCZI functionality for reading (subset of) Zeiss CZI files and meta-data.
- Aiohttp: a http client/server for asyncio.
- Akima: interpolation.
- Annoy: approximate nearest neighbors optimized for memory usage and loading/saving to disk.
- APSW: another Python SQLite wrapper.
- Arctic: a high performance datastore for time series and tick data.
- Aspell-python: bindings for GNU Aspell.
Using the LyX fork.
Extract the dictionaries to C:\ProgramData\Aspell\Dictionaries.
- Assimulo: a package for solving ordinary differential equations.
Requires numpy+mkl.
- Astropy: a core package for astronomy.
- Atom: memory efficient Python objects.
This package conflicts with Google's gdata.
- Autobahn: WebSocket & WAMP for Python on Twisted and asyncio.
- AutoPy: a GUI automation toolkit.
- Babel: tools for internationalizing Python applications.
- Backports.lzma: a backport of Python 3.3's lzma module.
- backports.zoneinfo: backport of the standard library module zoneinfo.
- Basemap: a matplotlib toolkit for plotting 2D data on maps based on GEOS.
Requires pyproj.
- Bazaar: a version control system.
- Bcolz: columnar and compressed data containers.
- Bfloat16: adds a bfloat16 dtype that supports most common numpy operations.
- Bigfloat: arbitrary precision correctly-rounded floating point arithmetic, via MPFR.
Superseded by gmpy2.
- Bintrees: Binary- RedBlack- and AVL-Trees.
- Bio_formats (experimental): a JCC generated wrapper for the Bio-Formats and SCIFIO Java libraries.
Requires Java SE 8 and JVM.DLL in the PATH.
- Biopython: a set of tools for biological computation.
- Bitarray: an object type which efficiently represents an array of booleans.
- Bitshuffle: filter for improving compression of typed binary data.
- Blaze: translates NumPy/Pandas-like syntax to systems like databases.
- Blis: the Blis BLAS-like linear algebra library, as a self-contained C-extension.
- Blist: a list-like type with better performance for large lists.
- Blosc: a high performance compressor optimized for binary data.
- Blosc2: a fast, compressed and persistent data store library.
- Blz: a chunked, compressed, data container (for memory and disk).
- Boost-histogram: bindings for the C++14 Boost::Histogram library.
- Boost.Python: enables seamless interoperability between C++ and Python.
- Bottleneck: fast NumPy array functions written in C.
- Brotli: a compression format.
- brotlipy: bindings to the Brotli compression library.
- Bsddb3: bindings for the Oracle Berkeley DB database. Linked to db-5.3.28.
- Bsdiff4: binary diff and patch using the BSDIFF4-format.
- BTrees: scalable persistent object containers.
- Cairocffi: CFFI-based bindings for the cairo graphics library.
GDK-PixBuf is not supported by this distribution.
- Cantera: a tool suite for chemical kinetics, thermodynamics, and transport.
Requires numpy+mkl.
- Carray: a chunked data container that can be compressed in-memory.
- Cartopy: a library providing cartographic tools.
- Casa_formats_io: implements I/O for CASA data formats.
- Casuarius: bindings for the Cassowary constraint solving toolkit.
- Caterva: a multidimensional data container on top of Blosc2.
- cChardet: a universal character encoding detector - binding to libcharsetdetect.
- Cdecimal: a package for correctly-rounded arbitrary precision decimal floating point arithmetic.
- celiagg: Anti-Grain Geometry for Python with Cython.
- CellCognition: an image analysis framework for fluorescence time-lapse microscopy.
Requires numpy+mkl, scipy, matplotlib, pyqt4, libsvm, vigra, qimage2ndarray, h5py, pandas and scikit-learn.
- CellProfiler: software for quantitative analysis of biological images.
Requires numpy+mkl, scipy, matplotlib, wxpython, h5py, vigra, mysqldb, pillow, and whatnot.
- Centrosome: an open source image processing library.
- ceODBC: enables access to databases using the ODBC API.
- Cf-units: units of measure as required by the Climate and Forecast (CF) metadata conventions.
- Cffi: a Foreign Function Interface for calling C code.
Requires pycparser.
- Cftime: time-handling functionality from netcdf4-python.
- CGAL-bindings: bindings for the Computational Geometry Algorithms Library.
- Cgkit: the Computer Graphics Kit, is useful for dealing with 3D data of any kind.
- Cgohlke: modules developed by Christoph Gohlke.
This meta-package installs
akima,
chebyfit,
cmapfile,
czifile,
dnacurve,
fcsfiles,
fmkr,
imagecodecs,
imagecodecs-lite,
imreg,
lfdfiles,
lucam,
molmass,
netpbmfile,
oiffile,
psf,
qdafile,
sdtfile,
tifffile,
transformations,
uciwebauth, and
vidsrc.
- Chaco: building interactive and custom 2-D plots.
Part of the Enthought Tool Suite.
- Chebyfit: fit multiple exponential and harmonic functions using Chebyshev polynomials.
- Cheetah: a template engine and code generation tool.
- Chompack: a library for chordal matrix computations.
- CLD: wraps Chromium's Compact Language Detector library.
- Cmapfile: write Chimera map (CMAP) files.
Requires tifffile, oiffile, scipy, and h5py.
- Cmarkgfm: bindings to GitHub's fork of cmark.
- COBRA: a package for constraints-based modeling of biological networks.
- Coverage: measures code coverage of programs during test execution.
- Cramjam: bindings to de/compression algorithms in Rust.
- Crc16: calculates CRC16 (Cyclic Redundancy Check).
- Crcmod: computes Cyclic Redundancy Checks (CRC).
- Cupy: a NumPy-like API accelerated with CUDA.
Requires CUDA Toolkit and CUDNN.
- Curses: an extension based on the PDCurses library.
The +utf8 builds ignore the system locale, and treat all narrow-character strings as UTF-8.
- CVXcanon: common operations for convex optimization modeling tools.
- CVXOPT (experimental non-MKL icl build): a package for convex optimization.
Includes GSL, FFTW, and GLPK w/ MPIR modules.
Requires numpy+mkl.
- CVXPY: a modeling language for convex optimization problems.
Requires numpy+mkl, scipy, cvxopt, scs, ecos, and osqp.
- cx_Freeze: a set of scripts and modules for freezing Python scripts into executable.
- cx_Logging: interfaces for logging.
- cx_Oracle: an interface to the Oracle Database conforming to the Python DB API 2.0 specification.
- Cyassimp (oblolete): bindings for the Open Assimp Import Library.
- Cymem: Cython memory pool for RAII-style memory management.
- Cyordereddict: a Cython implementation of OrderedDict.
- Cyrasterize: OpenGL offscreen rasterizing.
- Cython: a language for writing Python C extensions.
- Cytoolz: high performance functional utilities.
- Czifile: read Carl Zeiss(r) ZISRAW (CZI) files.
Requires tifffile and imagecodecs.
- Daal4py: a convenient API to the Intel® Data Analytics Acceleration Library.
Requires numpy+mkl.
- Datrie: efficiently stores Trie.
- DAWG: DAWG(DAFSA)-based dictionary-like read-only objects.
- Debug-information-files: installs the Windows debug information files (*.PDB).
- Debugpy: implements the Debug Adapter Protocol.
- Delny: creates N-dimensional Delaunay triangulations using libqhull.
- Dipy: diffusion MR imaging.
- Discretize: discretization tools for finite volume and inverse problems.
- Dnacurve: DNA Curvature Analysis.
- DTAIdistance: distance measures for time series.
- Dubins: finds the shortest paths between configurations for the Dubins car.
- Dukpy: a simple JavaScript interpreter.
- Dulwich: a Git library.
- DyND (experimental): bindings to the libdynd C++ dynamic ndarray library.
- ECOS: Embedded Conic Solver.
- Edt (GPL): multi-label anisotropic euclidean distance transform 3D.
- Elasticdeform: differentiable elastic deformations for N-dimensional images.
- Enable: low-level drawing and interaction.
Part of the Enthought Tool Suite.
- Enaml: a programming language and framework for creating user interfaces with minimal effort.
Requires atom, kiwisolver, pyqt4, and PLY.
- Entropy: fast entropy calculation.
- ETS: the Enthought Tool Suite is a collection of components for building scientific applications.
Requires chaco, traits, enable, scimath, and mayavi.
- FabIO: a IO library for images produced by 2D X-ray detector.
- Fann2: bindings for Fast Artificial Neural Networks Library.
- Fast-histogram: fast 1D and 2D histogram functions.
- Fastcache: a C implementation of the Python 3 lru_cache.
- Fastcluster: fast hierarchical clustering routines.
- Fastparquet: an implementation of the parquet columnar file format.
- Fastremap (LGPL): remap, mask, renumber, unique, and in-place transposition of 3D labeled images.
- Fastrlock: a fast RLock implementation.
- fastText: a library for fast text representation and classification.
- fastTSNE (discontinued): a fast, parallel implementations of t-SNE.
- Faulthandler: displays the Python traceback on a crash.
- Fcsfiles: read fluorescence correlation spectroscopy (FCS) data files.
- Fdint: Fermi-Dirac integrals of integer and half integer order.
- Ffnet: a feed-forward neural network.
- Fiona: OGR's neater API.
Requires GDAL.
- Fisher: an implementation of the Fisher's exact test.
- Fisx: an enhanced C++ port of the Physics routines used by PyMca.
- FLANN: a library for performing fast approximate nearest neighbor searches in high dimensional spaces.
- Fmkr: access FileMaker(tm) Server databases via XML publishing interface.
- Fonttools: manipulate font files.
- Fpzip: lossless compression for 3 and 4 dimensional floating point data.
- FreeImageDLL (deprecated): installs the FreeImage DLL to sys.prefix.
- FreeSASA: bindings for the FreeSASA C Library.
- FreeTypePy: bindings for the FreeType font rendering library.
- Friture: a program designed to analyze audio input in real-time.
Requires numpy, pyaudio, pyqt4, pyqwt, and pyopengl.
- Frozenlist: a list-like structure which implements collections.abc.MutableSequence.
- GDAL: the Geospatial Data Abstraction Library is a translator library for raster geospatial data formats.
This distribution includes a complete GDAL installation. Do not use together with OSGeo4W or gdalwin32.
Built with KML, HDF5, NetCDF, SpatiaLite, PostGIS, GEOS, PROJ etc.
The FileGDB plugin requires Esri's FileGDB API 1.3 or FileGDB 1.5 VS2015.
Requires VCredist SP1 on Python 2.7.
- Genshi: a toolkit for generation of output for the web.
- Gensim: a framework for fast Vector Space Modelling.
- Gevent: a coroutine-based networking library based on greenlet and libev.
Requires greenlet.
- GitDB: IO of git-style object databases.
- GLFW: bindings for GLFW, a library for OpenGL, OpenGL ES, and Vulkan.
- Glumpy: a natural interface between numpy and modern OpenGL.
Requires numpy, triangle and pyopengl.
- Glymur: interface to the OpenJPEG library to read and write JPEG 2000 files.
- GMPY: supports fast multiple-precision arithmetic.
Wraps the MPIR, MPFR, and MPC libraries.
- Goertzel-FFT: implements the Goertzel algorithm.
- Google-crc32c: implements the CRC32C hashing algorithm.
- GPy: a Gaussian processes framework.
- GR (discontinued): a universal framework for cross-platform visualization applications.
- Grako: a generator of PEG/Packrat parsers from EBNF grammars.
Superseded by TatSu.
- Greenlet: allows lightweight in-process concurrent programming.
- gRPCio: a HTTP/2-based Remote Procedure Call (RPC) framework.
- GuiQwt: an efficient 2D plotting library.
- Gvar: utilities for manipulating correlated Gaussian random variables.
- H5py: a general-purpose interface to the HDF5 library.
- HDBSCAN: a high performance implementation of HDBSCAN clustering.
- HDDM: Hierarchical Bayesian estimation of Drift Diffusion Models.
- HDF5plugin: a set of compression filters for h5py.
- Heatmap: create heatmaps.
- Hmmlearn: aglorithms and models to learn HMMs (hidden markov models).
- HoloPy (unstable): a tool for working with digital holograms and light scattering.
- HTSeq: infrastructure to process data from high-throughput sequencing assays.
- HyperSpy: multidimensional data analysis.
- ICSdll: an interface to the image correlation spectroscopy library ICSx64.dll.
- Igraph: an interface to the igraph high performance graph library.
Requires pycairo.
- Ilastik: an interactive learning and segmentation toolkit.
- Imagecodecs: image transformation, compression, and decompression codecs.
- Imagecodecs-lite (deprecated): a subset of imagecodecs.
- ImageD11: a software package for the analysis of 2D diffraction images.
- Imgui: bindings for the amazing Dear ImGui library.
- Iminuit: an interactive mimizer based on MINUIT.
- Imread: read images into numpy arrays.
- Imreg: FFT based image registration.
- Indexed_gzip: fast random access of gzip files.
- Intbitset: an intbitset data object.
- IOCBio: open-source software from the Laboratory of Systems Biology.
Requires numpy+mkl.
- Iris: a library for analysing and visualising meteorological and oceanographic data sets
Requires scipy, netcdf4-python, cartopy, shapely, cf-units, pyke, and whatnot.
- Javabridge: a wrapper for the Java Native Interface.
- JCC: a C++ code generator that produces a C++ object interface wrapping a Java library via Java's Native Interface (JNI).
Users must adjust "jcc/config.py" for the target system.
- Jellyfish: a library for doing approximate and phonetic matching of strings.
- Jpegio: a package for accessing the internal variables of the JPEG file format.
- JPype: allows full access to Java class libraries.
- Jsonlib: a JSON serializer/deserializer.
- JsonObject: a simple JSON-object mapping.
- Jupyter: an interactive computing environment.
Some functions require setuptools, pyzmq, tornado, pygments, markupsafe, jinja2, mistune, rpy2, pycairo, matplotlib, pyqt4 or pyside, pandoc, and whatnot.
- Kapteyn: modules for astronomical applications.
- Kivy: a library for developing multi-touch applications.
- Kiwisolver: an efficient implementation of the Cassowary constraint solving algorithm.
- Kwant: quantum transport simulations made easy.
Requires numpy+mkl and tinyarray.
- La: aka larry, the labeled numpy array.
- Lazy_object_proxy: a fast and thorough lazy object proxy.