Physical quantities module
Pint: makes units easy
Pint is a Python package to define, operate and manipulate physical quantities: the product of a numerical value and a unit of measurement. It allows arithmetic operations between them and conversions from and to different units.
It is distributed with a comprehensive list of physical units, prefixes and constants. Due to its modular design, you can extend (or even rewrite!) the complete list without changing the source code. It supports a lot of numpy mathematical operations without monkey patching or wrapping numpy.
It has a complete test coverage. It runs in Python 2.6 and 3.X with no other dependency. It is licensed under BSD.
It is extremely easy and natural to use:
>>> import pint >>> ureg = pint.UnitRegistry() >>> 3 * ureg.meter + 4 * ureg.cm <Quantity(3.04, 'meter')>
and you can make good use of numpy if you want:
>>> import numpy as np >>> [3, 4] * ureg.meter + [4, 3] * ureg.cm <Quantity([ 3.04 4.03], 'meter')> >>> np.sum(_) <Quantity(7.07, 'meter')>
To install Pint, simply:
$ pip install pint
or utilizing conda with, the conda-forge channel:
$ conda install -c conda-forge pint
and then simply enjoy it!
Full documentation is available at http://pint.readthedocs.org/
Although there are already a few very good Python packages to handle physical quantities, no one was really fitting my needs. Like most developers, I programed Pint to scratch my own itches.
- Unit parsing: prefixed and pluralized forms of units are recognized without explicitly defining them. In other words: as the prefix kilo and the unit meter are defined, Pint understands kilometers. This results in a much shorter and maintainable unit definition list as compared to other packages.
- Standalone unit definitions: units definitions are loaded from simple and easy to edit text file. Adding and changing units and their definitions does not involve changing the code.
- Advanced string formatting: a quantity can be formatted into string using PEP 3101 syntax. Extended conversion flags are given to provide latex and pretty formatting.
- Small codebase: small and easy to maintain with a flat hierarchy.
- Dependency free: it depends only on Python and its standard library.
- Python 2 and 3: A single codebase that runs unchanged in Python 2.6+ and Python 3.0+.
- Advanced NumPy support: While NumPy is not a requirement for Pint, when available ndarray methods and ufuncs can be used in Quantity objects.
Pint is written and maintained by Hernan E. Grecco <email@example.com>.
Other contributors, listed alphabetically, are:
- Aaron Coleman
- Alexander Böhn <firstname.lastname@example.org>
- Ana Krivokapic <email@example.com>
- Andrea Zonca <firstname.lastname@example.org>
- Brend Wanders <email@example.com>
- coutinho <firstname.lastname@example.org>
- Daniel Sokolowski <email@example.com>
- Dave Brooks <firstname.lastname@example.org>
- David Linke
- Ed Schofield <email@example.com>
- Eduard Bopp <firstname.lastname@example.org>
- Eli <email@example.com>
- Felix Hummel <firstname.lastname@example.org>
- Giel van Schijndel <email@example.com>
- James Rowe <firstname.lastname@example.org>
- Jim Turner <email@example.com>
- Joel B. Mohler <firstname.lastname@example.org>
- John David Reaver <email@example.com>
- Jonas Olson <firstname.lastname@example.org>
- Kaido Kert <email@example.com>
- Kenneth D. Mankoff <firstname.lastname@example.org>
- Kevin Davies <email@example.com>
- Luke Campbell <firstname.lastname@example.org>
- Matthieu Dartiailh <email@example.com>
- Nate Bogdanowicz <firstname.lastname@example.org>
- Peter Grayson <email@example.com>
- Richard Barnes <firstname.lastname@example.org>
- Ryan Dwyer <email@example.com>
- Ryan Kingsbury <RyanSKingsbury@alumni.unc.edu>
- Sundar Raman <firstname.lastname@example.org>
- Tiago Coutinho <email@example.com>
- Thomas Kluyver <firstname.lastname@example.org>
- Tom Ritchford <email@example.com>
- Virgil Dupras <firstname.lastname@example.org>
(If you think that your name belongs here, please let the maintainer know)
- Add support for datetime math. (Issue #510, thanks robertd)
- Fixed _repr_html_ in Python 2.7. (Issue #512)
- Implemented BaseRegistry.auto_reduce_dimensions. (Issue #500, thanks robertd)
- Fixed dimension compatibility bug introduced on Registry refactoring (Issue #523, thanks dalito)
- Refactored the Registry in multiple classes for better separation of concerns and clarity.
- Implemented support for defining multiple units per define call (one definition per line). (Issue #462)
- In pow and ipow, allow array exponents (with len > 1) when base is dimensionless. (Issue #483)
- Wraps now gets the canonical name of the unit when passed as string. (Issue #468)
- NumPy exp and log keeps the type (Issue #95)
- Implemented a function decorator to ensure that a context is active (with_context) (Issue #465)
- Add warning when a System contains an unknown Group. (Issue #472)
- Add conda-forge installation snippet. (Issue #485, thanks stadelmanma)
- Properly support floor division and modulo. (Issue #474, thanks tecki)
- Measurement Correlated variable fix. (Issue #463, thanks tadhgmister)
- Implement degree sign handling. (Issue #449, thanks iamthad)
- Change UndefinedUnitError to inherit from AttributeError (Issue #480, thanks jhidding)
- Simplified travis for faster testing.
- Fixed order units in siunitx formatting. (Issue #441)
- Changed Systems lister to return a list instead of frozenset. (Issue #425, thanks GloriaVictis)
- Fixed issue with negative values in to_compact() method. (Issue #443, thanks nowox)
- Improved defintions. (Issues #448, thanks gdonval)
- Improved Parser to support capital “E” on scientific notation. (Issue #390, thanks javenoneal)
- Make sure that prefixed units are defined on the registry when unplicking. (Issue #405)
- Automatic unit names translation through babel. (Issue #338, thanks alexbodn)
- Support pickling Unit objects. (Issue #349)
- Add support for wavenumber/kayser in spectroscopy context. (Issue #321, thanks gerritholl)
- Improved formatting. (thanks endolith and others)
- Add support for inline comments in definitions file. (Issue #366)
- Implement Unit.__deepcopy__. (Issue #357, thanks noahl)
- Allow changing shape for Quantities with numpy arrays. (Issue #344, thanks tecki)
- Fixed backward incompatibility problem when parsing dimensionless units.
- Use NIST as source for most of the unit information.
- Added message to assertQuantityEqual.
- Added detection of circular dependencies in definitions.
- Added Systems and groups. (Issue #215, #315)
- Implemented references for wraps decorator. (Issue #195)
- Added check decorator to UnitRegistry. (Issue #283, thanks kaidokert)
- Added compact conversion. (See #224, thanks Ryan Dwyer)
- Added compact formating code. (Issue #240)
- New Unit Class. (thanks Matthieu Dartiailh)
- Refactor UnitRegistry. (thanks Matthieu Dartiailh)
- Move definitions, errors, and converters into their own modules. (thanks Matthieu Dartiailh)
- UnitsContainer is now immutable (Issue #202, thanks Matthieu Dartiailh)
- New parser and evaluator. (Issue #226, thanks Aaron Coleman)
- Added support for Unicode identifiers.
- Added m_as as way top retrieve the magnitude in different units. (Issue #227)
- Added Short form for magnitude and units. (Issue #234)
- Improved deepcopy. (Issue #252, thanks Emilien Kofman)
- Improved testing infrastructure.
- Improved docs. (thanks Ryan Dwyer, Martin Thoma, Andrea Zonca)
- Fixed short names on electron_volt and hartree.
- Fixed definitions of scruple and drachm. (Issue #262, thanks takowl)
- Fixed troy ounce to 480 ‘grains’. (thanks elifab)
- Added ‘quad’ as a unit of energy (= 10**15 Btu). (thanks Ed Schofield)
- Added “hectare” as a supported unit of area and ‘ha’ as the symbol for hectare. (thanks Ed Schofield)
- Added peak sun hour and Langley. (thanks Ed Schofield)
- Added photometric units: lumen & lux. (Issue #230, thanks janpipek)
- A fraction magnitude quantity is conserved (Issue #323, thanks emilienkofman)
- Improved conversion performance by removing unnecessart try/except. (Issue #251)
- Added to_tuple and from_tuple to facilitate serialization.
- Fixed support for NumPy 1.10 due to a change in the Default casting rule (Issue #320)
- Infrastructure: Added doctesting.
- Infrastructure: Better way to specify exclude matrix in travis.
- Fix operations with measurments and user defined units. (Issue #204)
- Faster conversions through caching and other performance improvements. (Issue #193, thanks MatthieuDartiailh)
- Better error messages on Quantity.__setitem__. (Issue #191)
- Fixed abbreviation of fluid_ounce. (Issue #187, thanks hsoft)
- Defined Angstrom symbol. (Issue #181, thanks JonasOlson)
- Removed fetching version from git repo as it triggers XCode installation on OSX. (Issue #178, thanks deanishe)
- Improved context documentation. (Issue #176 and 179, thanks rsking84)
- Added Chemistry context. (Issue #179, thanks rsking84)
- Fix help(UnitRegisty) (Issue #168)
- Optimized “get_dimensionality” and “get_base_name”. (Issue #166 and #167, thanks jbmohler)
- Renamed ureg.parse_units parameter “to_delta” to “as_delta” to make clear. that no conversion happens. Accordingly, the parameter/property “default_to_delta” of UnitRegistry was renamed to “default_as_delta”. (Issue #158, thanks dalit)
- Fixed problem when adding two uncertainties. (thanks dalito)
- Full support for Offset units (e.g. temperature) (Issue #88, #143, #147 and #161, thanks dalito)
- Changed travis config to use miniconda for faster testing.
- Added wheel configuration to setup.cfg.
- Ensure resource streams are closed after reading.
- Require setuptools. (Issue #169)
- Implemented real, imag and T Quantity properties. (Issue #171)
- Implemented __int__ and __long__ for Quantity (Issue #170)
- Fixed SI prefix error on ureg.convert. (Issue #156, thanks jdreaver)
- Fixed parsing of multiparemeter contexts. (Issue #174)
- Implemented a standard way to change the registry used in unpickling operations. (Issue #148)
- Fix bug where conversion would fail due to caching. (Issue #140, thanks jdreaver)
- Allow assigning Not a Number to a quantity array. (Issue #127)
- Decoupled Quantity in place and not in place unit conversion methods.
- Return None in functions that modify quantities in place.
- Improved testing infrastructure to check for unwanted warnings.
- Added test function at the package level to run all tests.
- Improved test suite helper functions.
- Print honors default format w/o format(). (Issue #132, thanks mankoff)
- Fixed sum() by treating number zero as a special case. (Issue #122, thanks rec)
- Improved behaviour in ScaleConverter, OffsetConverter and Quantity.to. (Issue #120)
- Reimplemented loading of default definitions to allow Pint in a cx_freeze or similar package. (Issue #118, thanks jbmohler)
- Implemented parsing of pretty printed units. (Issue #117, thanks jpgrayson)
- Fixed representation of dimensionless quantities. (Issue #112, thanks rec)
- Raise error when invalid formatting code is given. (Issue #111, thanks rec)
- Default registry to lazy load, raise error on redefinition (Issue #108, thanks rec, aepsil0n)
- Added condensed format. (Issue #107, thanks rec)
- Added UnitRegistry () operator to parse expression replacing . (Issue #106, thanks rec)
- Optional case insensitive unit parsing. (Issue #105, thanks rec, jeremyfreeman, dbrnz)
- Change the Quantity mutability depending on magnitude type. (Issue #104, thanks rec)
- Implemented API to list compatible units. (Issue #89)
- Implemented cache of key UnitRegistry methods.
- Rewrote the Measurement class to use uncertainties. (Issue #24)
- Python 2.6 support (Issue #96, thanks tiagocoutinho)
- Fixed symbol for inch. (Issue #102, thanks cybertoast)
- Stop raising AttributeError when wrapping funcs without all of the attributes. (Issue #100, thanks jturner314)
- Fixed warning appearing in Py2.x when comparing a Numpy Array with an empty string. (Issue #98, thanks jturner314)
- Add links to AUR packages in docs. (Issue #91, thanks jturner314)
- Fixed garbage collection related problem. (Issue #92, thanks jturner314)
- Integer Division with Arrays. (Issue #80, thanks jdreaver)
- Improved Documentation. (Issue #83, thanks choloepus)
- Removed ‘h’ alias for hour due to conflict with Planck’s constant. (Issue #82, thanks choloepus)
- Improved get_base_units for non-multiplicative units. (Issue #85, thanks exxus)
- Refactored code for multiplication. (Issue #84, thanks jturner314)
- Removed ‘R’ alias for roentgen as it collides with molar_gas_constant. (Issue #87, thanks rsking84)
- Improved naming of temperature units and multiplication of non-multiplicative units. (Issue #86, tahsnk exxus)
- Introduced Contexts: relation between incompatible dimensions. (Issue #65)
- Fixed get_base_units for non multiplicative units. (Related to issue #66)
- Implemented default formatting for quantities.
- Changed comparison between Quantities containing NumPy arrays. (Issue #75) - BACKWARDS INCOMPATIBLE CHANGE
- Fixes for NumPy 1.8 due to changes in handling binary ops. (Issue #73)
- ParseHelper can now parse units named like python keywords. (Issue #69)
- Fix comparison of quantities. (Issue #74)
- Fix Inequality operator. (Issue #70, thanks muggenhor)
- Improved travis configuration. (thanks muggenhor)
- Fix get_dimensionality for non multiplicative units. (Issue #66)
- Proper handling of @import directive inside a file read using pkg_resources. (Issue #68)
- fix right division on python 2.7 (Issue #58, thanks natezb)
- fix formatting of fractional exponentials between 0 and 1. (Issue #62, thanks jdreaver)
- fix installation as egg. (Issue #61)
- fix handling of strange values as input of Quantity. (Issue #53)
- math operations between quantities of different registries now raise a ValueError. (Issue #52)
- support for IPython autocomplete and rich display. (Issues #30 and #31)
- support for @import directive in definitions file. (Issue #22)
- support for wrapping functions to make them pint-aware. (Issue #16)
- support for comparing UnitsContainer to string. (Issue #35)
- fix error raised while converting from a single unit to one expressed as the relation between many. (Issue #29)
- fix error raised when unit symbol is missing. (Issue #41)
- fix error raised when magnitude is Decimal. (Issue #46, thanks danielsokolowski)
- support for non-installed pint. (Issue #42, thanks danielsokolowski)
- support for application of numpy function on non-ndarray magnitudes. (Issue #44)
- support for math operations on dimensionless Quantities (written with units). (Issue #45)
- fix obtaining dimensionless quantity from string. (Issue #50)
- fix adding and comparing numbers to a dimensionless quantity (written with units). (Issue #54)
- Support for iter in Quantity. (Issue #55, thanks natezb)
- fix error raised while converting from a single unit to one expressed as the relation between many. (Issue #29)
- support for Measurement (Quantity +/- error).
- implemented buckingham pi theorem for dimensional analysis.
- support for temperature units and temperature difference units.
- parser can infers if the user mean temperature or temperature difference.
- support for derived dimensions (e.g. [speed] = [length] / [time]).
- refactored the code into multiple files.
- refactored code to isolate definitions and converters.
- refactored formatter out of UnitParser class.
- added tox and travis config files for CI.
- comprehensive NumPy testing including almost all ufuncs.
- full NumPy support (features is not longer experimental).
- fixed bug preventing from having independent registries. (Issue #10, thanks bwanders)
- forces real division as default for Quantities. (Issue #7, thanks dbrnz)
- improved default unit definition file. (Issue #13, thanks r-barnes)
- smarter parser supporting spaces as multiplications and other nice features. (Issue #13, thanks r-barnes)
- moved testsuite inside package.
- short forms of binary prefixes, more units and fix to less than comparison. (Issue #20, thanks muggenhor)
- pint is now zip-safe (Issue #23, thanks muggenhor)
Version 0.1.3 (2013-01-07)
- abbreviated quantity string formating.
- complete Python 2.7 compatibility.
- implemented pickle support for Quantities objects.
- extended NumPy support.
- various bugfixes.
Version 0.1.2 (2012-08-12)
- experimenal NumPy support.
- included default unit definitions file. (Issue #1, thanks fish2000)
- better testing.
- various bugfixes.
- fixed some units definitions. (Issue #4, thanks craigholm)
Version 0.1.1 (2012-07-31)
- better packaging and installation.
Version 0.1 (2012-07-26)
- first public release.