# History¶

## 2.8.0 (2020-10-05)¶

• Dropped support for Python 3.5.
• Add delta_degC and delta_degF units to support temperature difference arithmetic. See PR #152. Thank you to Lee Johnston (@l-johnston on GitHub) for the contribution.
• Fix an issue where a subsequent load of the unit registry with units that are equal but not identical leads to a crash. See PR #158. Thank you to Matthew Turk (@matthewturk on GitHub) for the initial bug report and fix.
• Add force unit kip and pressure unit psi. Thank you to P. Talley (@otaithleigh on GitHub) for the contribution. See PR #162.
• Fix an issue where arithmetic operations on units defined in different registries and having the conversion defined in one direction would lead to a crash. See PR #164. Thank you to Clément Robert (@neutrinoceros on GitHub) for the initial bug report and fix.

## 2.7.2 (2020-06-29)¶

• The unyt.returns and unyt.accepts decorators now work correctly for functions that accept or return data with dimensionless units. See PR #146. Thank you to Simon Schopferer (@simfinite on GitHub) for the initial bug report and fix.
• Data used in the tests are packaged with the source distribution and unyt.test() is now itself run as part of unyt’s continuous integration tests. See PR #149 and PR #150. Thank you to Miguel de Val-Borro (@migueldvb on GitHub) for the initial bug report and fix.
• The degC and degF units now render as °C and °F by default, °C and °F are now recognized as valid unit names as well. Thank you to Lee Johnston (@l-johnston on GitHub) for the contribution.
• Use a more canonical representation of the micro symbol when printing units with the micro prefix, avoiding issues with displaying unit names in Matplotlib plot labels. See PR #153. Thank you to Matthew Turk (@matthewturk on GitHub) for the bug report and fix.
• Add more alternative spellings for solar units. See PR #155. Thank you to Clément Robert (@neutrinoceros on GitHub) for the initial bug report.

## 2.7.1 (2020-02-17)¶

• Fix compatibility with unyt_array subclasses that do not have the new name argument in their initializer. See PR #140.
• Fix an issue where custom units added to a unit registry were not restored correctly when reloading a unit registry from a JSON or pickle representation. See PR #140.

## 2.7.0 (2020-02-06)¶

• The unyt_array and unyt_quantity classes now have a new, optional name attribute. The primary purpose of this attribute is to enable automatic generation of matplotlib plot labels. The name attribute is propagated through unit conversions and copies but is not propagated through mathematical operations. See PR #129 and the documentation for details.
• Add support for the Neper and Bel units with logarithmic dimensions. This includes support for the decibel unit. Note that logarithmic units can only be used with other logarithmic units and must be applied and stripped manually. See PR #133 and PR #134.
• Add support for the SI unit of inductance, H. See PR #135.
• Fix formatting of error message produced when raising a quantity to a power with units. See PR #131. Thank you to Lee Johnston (@l-johnston on GitHub) for all of the above contributions.
• Fix incorrect unit metadata when loading a pickled array saved by yt.units. See PR #137.

## 2.6.0 (2020-01-22)¶

• Matplotlib support is no longer enabled by importing unyt. Instead, it is now necessary to use the unyt.matplotlib_support context manager in code where you want unyt to automatically generate plot labels. Enabling Matplotlib support by default in the previous release caused crashes in previously working code for some users so we have decided to make the plotting support optional. See the documentation for more details. We are sorry for introducing a new feature that broke some user’s code. See PR #126. Thank you to Lee Johnston (@l-johnston on GitHub) for the contribution.
• Updated the contribution guide to include more details about setting up multiple Python versions for the tox tests.

## 2.5.0 (2020-01-20)¶

• Importing unyt now registers unyt with Matplotlib’s interface for handling units. See the Matplotlib and unyt documentation for more details. See PR #122 and PR #124. Thank you to Lee Johnston (@l-johnston on GitHub) for the contribution.
• Updated the LaTeX formatting of solar units so they do not get rendered italicized. See PR #120. Thank you to Josh Borrow (@JBorrow on GitHub) for the contribution.
• Reduce floating point round-off error when data are converted from integer to float dtypes. See PR #119.

## 2.4.1 (2020-01-10)¶

• Add support for the latest releases of h5py, sympy, NumPy, and PyTest. See PR #115.
• Fix the hash implementation so that identical units cannot have distinct hashes. See PR #114 and PR #117. Thank you to Ben Kimock (@saethlin on GitHub) for the contribution.

## 2.4.0 (2019-10-25)¶

• Improve performance for creating quantities or small arrays via multiplication with a unit object. Creating an array or quantity from data that does not have a numeric dtype will now raise UnitOperationError instead of UnitDtypeError, which has been removed. See PR #111.
• Comparing data with units that have different dimensions using the == and != operators will no longer raise an error. Other comparison operators will continue to raise errors. See PR #109.
• Fixed a corner case in the implementation of clip. See PR #108. Thank you to Matthew Turk (@matthewturk on GitHub) for the contribution.
• Added % as a valid dimensionless unit with a value of 0.01, also available under the name percent. See PR #106. Thank you to Thomas Hisch for the contribution.
• Added bar to the default unit lookup table. See PR #103. Thank you to Thomas Hisch (@thisch on GitHub) for the contribution.

## 2.3.1 (2019-08-21)¶

• Added support for the clip ufunc added in NumPy 1.17. See PR #102.

## 2.3.0 (2019-08-14)¶

• Added unyt.dimensions.accepts and unyt.dimensions.returns, decorators that can be used to ensure that data passed into a decorated function has units that are dimensionally consistent with the function’s expected inputs. See PR #98. Thank you to Andrei Berceanu (@berceanu on GitHub) for the contribution.
• Added unyt.allclose_units and improved documentation for writing tests for code that uses unyt. This is a wrapper for numpy.allclose that also checks the units of the input arrays. See PR #94. Thank you to Andrei Berceanu (@berceanu on GitHub) for the contribution.

## 2.2.2 (2019-07-03)¶

• Fix erroneous conversions of E&M units to their “native” unit system, for example, converting Gauss to CGS units would return Tesla and converting Tesla to MKS units would return Gauss. See PR #96.

## 2.2.1 (2019-07-02)¶

• Add support for loading JSON unit registries saved by yt.units. See PR #93.
• Correct the value of the light_year unit. See PR #93.
• It is now possible to define a UnitSystem object with a quantity. See PR #86.
• Incorrect units for Planck units have been fixed. See PR #85. Thank you to Nathan Musoke (@musoke on GitHub) for the contribution.
• Updated value of Newton’s constant to latest CODATA value. See PR #84.

## 2.2.0 (2019-04-03)¶

• Several performance optimizations. This includes a slight change to the behavior of MKS/CGS E&M unit conversions that makes the conversion rules slightly more relaxed. See PR #82.

## 2.1.1 (2019-03-27)¶

• Fixed an issue with restoring unit registries from JSON output. See PR #81.

## 2.1.0 (2019-03-26)¶

This release includes a few minor new features and bugfixes for the 2.0.0 release.

• Added support for the matmul @ operator. See PR #80.
• Allow defining unit systems using Unit instances instead of string unit names. See PR #71. Thank you to Josh Borrow (@JBorrow on GitHub) for the contribution.
• Fix incorrect behavior when uhstack is called with the axis argument. See PR #73.
• Add "rsun", "lsun", and "au" as alternate spellings for the "Rsun", "Lsun", and "AU" units. See PR #77.
• Improvements for working with code unit systems. See PR #78.
• Reduce impact of floating point round-off noise on unit comparisons. See PR #79.

## 2.0.0 (2019-03-08)¶

unyt 2.0.0 includes a number of exciting new features as well as some bugfixes. There are some small backwards incompatible changes in this release related to automatic unit simplification and handling of dtypes. Please see the release notes below for more details. If you are upgrading from unyt 1.x we suggest testing to make sure these changes do not siginificantly impact you. If you run into issues please let us know by opening an issue on GitHub.

• Dropped support for Python 2.7 and Python 3.4. Added support for Python 3.7.

• Added Unit.simplify(), which cancels pairs of terms in a unit expression that have inverse dimensions and made it so the results of unyt_array multiplication and division will automatically simplify units. This means operations that combine distinct dimensionally equivalent units will cancel in many situations. For example

>>> from unyt import kg, g
>>> print((12*kg)/(4*g))
3000.0 dimensionless


older versions of unyt would have returned 4.0 kg/g. See PR #58 for more details. This change may cause the units of operations to have different, equivalent simplified units than they did with older versions of unyt.

• Added the ability to resolve non-canonical unit names to the equivalent canonical unit names. This means it is now possible to refer to a unit name using an alternative non-canonical unit name when importing the unit from the unyt namespace as well as when a unit name is passed as a string to unyt. For example:

>>> from unyt import meter, second
>>> data = 1000.*meter/second
>>> data.to('kilometer/second')
unyt_quantity(1., 'km/s')
>>> data.to('metre/s')
unyt_quantity(1000., 'm/s')


The documentation now has a table of units recognized by unyt along with known alternative spellings for each unit.

• Added support for unicode unit names, including μm for micrometer and Ω for ohm. See PR #59.

• Substantially improved support for data that does not have a float64 dtype. Rather than coercing all data to float64 unyt will now preserve the dtype of data. Data that is not already a numpy array will be coerced to a dtype by calling np.array internally. Converting integer data to a new unit will convert the data to floats, if this causes a loss of precision then a warning message will be printed. See PR #55 for details. This change may cause data to be loaded into unyt with a different dtype. On Windows the default integer dtype is int32, so data may begin to be recognized as int32 or converted to float32 where before it was interpreted as float64 by default.

• Unit registries are now associated with a unit system. This means that it’s possible to create a unit registry that is associated with a non-MKS unit system so that conversions to “base” units will end up in that non-MKS system. For example:

>>> from unyt import UnitRegistry, unyt_quantity
>>> ureg = UnitRegistry(unit_system='cgs')
>>> data = unyt_quantity(12, 'N', registry=ureg)
>>> data.in_base()
unyt_quantity(1200000., 'dyn')


See PR #62 for details.

• Added two new utility functions, unyt.unit_systems.add_constants and unyt.unit_systems.add_symbols that can populate a namespace with a set of unit symbols in the same way that the top-level unyt namespace is populated. For example, the author of a library making use of unyt could create an object that users can use to access unit data like this:

>>> from unyt.unit_systems import add_symbols
>>> from unyt.unit_registry import UnitRegistry
>>> class UnitContainer(object):
...    def __init__(self):
>>> units = UnitContainer()
>>> units.kilometer
km
>>> units.microsecond
μs


See PR #68.

• The unyt codebase is now automatically formatted by black. See PR #57.

• Add missing “microsecond” name from top-level unyt namespace. See PR #48.

• Add support for numpy.argsort by defining unyt_array.argsort. See PR #52.

• Add Farad unit and fix issues with conversions between MKS and CGS electromagnetic units. See PR #54.

• Fixed incorrect conversions between inverse velocities and statohm. See PR #61.

• Fixed issues with installing unyt from source with newer versions of pip. See PR #63.

• Fixed bug when using define_unit that caused crashes when using a custom unit registry. Thank you to Bili Dong (@qobilidob on GitHub) for the pull request. See PR #64.

We would also like to thank Daniel Gomez (@dangom), Britton Smith (@brittonsmith), Lee Johnston (@l-johnston), Meagan Lang (@langmm), Eric Chen (@ericchen), Justin Gilmer (@justinGilmer), and Andy Perez (@sharkweek) for reporting issues.

## 1.0.7 (2018-08-13)¶

Trigger zenodo archiving.

## 1.0.6 (2018-08-13)¶

Minor paper updates to finalize JOSS submission.

## 1.0.5 (2018-08-03)¶

unyt 1.0.5 includes changes that reflect the peew review process for the JOSS method paper. The peer reviewers were Stuart Mumfork (@cadair), Trevor Bekolay (@tbekolay), and Yan Grange (@ygrange). The editor was Kyle Niemeyer (@kyleniemeyer). The unyt development team thank our reviewers and editor for their help getting the unyt paper out the door as well as for the numerous comments and suggestions that improved the paper and package as a whole.

In addition we’d like to thank Mike Zingale, Meagan Lang, Maksin Ratkin, DougAJ4, Ma Jianjun, Paul Ivanov, and Stephan Hoyer for reporting issues.

• Added docstrings for the custom exception classes defined by unyt. See PR #44.
• Added improved documentation to the contributor guide on how to run the tests and what the PR review guidelines are. See PR #43.
• Updates to the text of the method paper in response to reviewer suggestions. See PR #42.
• It is now possible to run the tests on an installed copy of unyt by executing unyt.test(). See PR #41.
• Minor edit to LICENSE file so GitHub recognizes it. See PR #40. Thank you to Kyle Sunden (@ksunden) for the contribution.
• Add spatial frequency as a dimension and added support in the spectral equivalence for the spatial frequency dimension. See PR #38 Thank you to Kyle Sunden (@ksunden) for the contribution.
• Add support for Python 3.7. See PR #37.
• Importing unyt will now fail if numpy and sympy are not installed. See PR #35
• Testing whether a unit name is contained in a unit registry using the Python in keyword will now work correctly for all unit names. See PR #31.
• The aliases for megagram in the top-level unyt namespace were incorrectly set to reference kilogram and now have the correct value. See PR #29.
• Make it possible to take scalars to dimensionless array powers with a properly broadcasted result without raising an error about units. See PR #23.
• Whether or not a unit is allowed to be SI-prefixable (for example, meter is SI-prefixable to form centimeter, kilometer, and many other units) is now stored as metadata in the unit registry rather than as global state inside unyt. See PR #21.
• Made adjustments to the rules for converting between CGS and MKS E&M units so that errors are only raised when going between unit systems and not merely when doing a complicated unit conversion invoving E&M units. See PR #20.
• round(q) where q is a unyt_quantity instance will no longer raise an error and will now return the nearest rounded float. See PR #19.
• Fixed a typo in the readme. Thank you to Paul Ivanov (@ivanov) for the fix.
• Added smoot as a unit. See PR #14.

## 1.0.4 (2018-06-08)¶

• Expand installation instructions
• Mention paper and arxiv submission in the readme.

## 1.0.3 (2018-06-06)¶

• Fix readme rendering on pypi

## 1.0.2 (2018-06-06)¶

• Added a paper to be submitted to the Journal of Open Source Software.