astropy v4.3 Release Notes

Release Date: 2021-07-26 // about 1 year ago
  • πŸ†• New Features


    • Change padding sizes for fft_pad in convolve_fft from powers of 2 only to scipy-optimized numbers, applied separately to each dimension; yielding some performance gains and avoiding potential large memory impact for certain multi-dimensional inputs. [#11533]


    • βž• Adds the ability to create topocentric CIRS frames. Using these, AltAz calculations are now accurate down to the milli-arcsecond level. [#10994]

    • βž• Adds a direct transformation from ICRS to AltAz frames. This provides a modest speedup of approximately 10 percent. [#11079]

    • βž• Adds new WGS84GeodeticRepresentation, WGS72GeodeticRepresentation, and GRS80GeodeticRepresentation. These are mostly for use inside EarthLocation but can also be used to convert between geocentric (cartesian) and different geodetic representations directly. [#11086]

    • SkyCoord.guess_from_table now also searches for differentials in the table. In addition, multiple regex matches can be resolved when they are exact component names, e.g. having both columns β€œdec” and β€œpm_dec” no longer errors and will be included in the SkyCoord. [#11417]

    • All representations now have a transform method, which allows them to be transformed by a 3x3 matrix in a Cartesian basis. By default, transformations are routed through CartesianRepresentation. SphericalRepresentation and PhysicssphericalRepresentation override this for speed and to prevent NaN leakage from the distance to the angular components. Also, the functions is_O3 and is_rotation have been added to matrix_utities for checking whether a matrix is in the O(3) group or is a rotation (proper or improper), respectively. [#11444]

    • 🚚 Moved angle formatting and parsing utilities to astropy.coordinates.angle_formats. Added new functionality to astropy.coordinates.angle_utilities for generating points on or in spherical surfaces, either randomly or on a grid. [#11628]

    • Added a new method to SkyCoord, spherical_offsets_by(), which is the conceptual inverse of spherical_offsets_to(): Given angular offsets in longitude and latitude, this method returns a new coordinate with the offsets applied. [#11635]

    • πŸ”¨ Refactor conversions between GCRS and CIRS,TETE for better accuracy and substantially improved speed. [#11069]

    • 🐎 Also refactor EarthLocation.get_gcrs for an increase in performance of an order of magnitude, which enters as well in getting observed positions of planets using get_body. [#11073]

    • πŸ”¨ Refactored the usage of metaclasses in astropy.coordinates to instead use __init_subclass__ where possible. [#11090]

    • Removed duplicate calls to transform_to from match_to_catalog_sky and match_to_catalog_3d, improving their performance. [#11449]

    • The new DE440 and DE440s ephemerides are now available via shortcuts 'de440' and 'de440s'. The DE 440s ephemeris will probably become the default ephemeris when chosing 'jpl' in 5.0. [#11601]


    • Cosmology parameter dictionaries now also specify the Cosmology class to which the parameters correspond. For example, the dictionary for astropy.cosmology.parameters.Planck18 has the added key-value pair ("cosmology", "FlatLambdaCDM"). [#11530] ^

    • βž• Added support for reading and writing ASCII tables in QDP (Quick and Dandy Plotter) format. [#11256]

    • βž• Added support for reading and writing multidimensional column data (masked and unmasked) to ECSV. Also added formal support for reading and writing object-type column data which can contain items consisting of lists, dicts, and basic scalar types. This can be used to store columns of variable-length arrays. Both of these features use JSON to convert the object to a string that is stored in the ECSV output. [#11569, #11662, #11720] ^

    • βž• Added append keyword to append table objects to an existing FITS file [#2632, #11149]

    • Check that the SIMPLE card is present when opening a file, to ensure that the file is a valid FITS file and raise a better error when opening a non FITS one. ignore_missing_simple can be used to skip this verification. [#10895]

    • πŸ”¦ Expose Header.strip as a public method, to remove the most common structural keywords. [#11174]

    • Enable the use of os.PathLike objects when dealing with (mainly FITS) files. [#11580]

    • Readers and writers can now set a priority, to assist with resolving which format to use. [#11214]

    • πŸ”– Version 1.4 VOTables now use the VOUnit format specification. [#11032]

    • When reading VOTables using the Unified File Read/Write Interface (i.e. using the or functions) it is now possible to specify all keyword arguments that are valid for [#11643]

    astropy.modeling ^

    • βž• Added a state attribute to models to allow preventing the synching of constraint values from the constituent models. This synching can greatly slow down fitting if there are large numbers of fit parameters. model.sync_constraints = True means check constituent model constraints for compound models every time the constraint is accessed, False, do not. Fitters that support constraints will set this to False on the model copy and then set back to True when the fit is complete before returning. [#11365]

    • The convolve_models_fft function implements model convolution so that one insures that the convolution remains consistent across multiple different inputs. [#11456]

    astropy.nddata ^

    • Prevent unnecessary copies of the data during NDData arithmetic when units need to be added. [#11107]

    • NDData str representations now show units, if present. [#11553]

    astropy.stats ^

    • βž• Added the ability to specify stdfunc='mad_std' when doing sigma clipping, which will use a built-in function and lead to significant performance improvements if cenfunc is 'mean' or 'median'. [#11664]

    • 🐎 Significantly improved the performance of sigma clipping when cenfunc and stdfunc are passed as strings and the grow option is not used. [#11219]

    • πŸ‘Œ Improved performance of bayesian_blocks() by removing one np.log() call [#11356]

    astropy.table ^

    • βž• Add table attributes to include or exclude columns from the output when printing a table. This functionality includes a context manager to include/exclude columns temporarily. [#11190]

    • πŸ‘Œ Improved the string representation of objects related to Table.indices so they now indicate the object type and relevant attributes. [#11333]


    • πŸ‘» An exception is raised when n_bins is passed as an argument while any of the parameters time_bin_start or time_bin_size is not scalar. [#11463]

    astropy.units ^

    • The physical_type attributes of each unit are now objects of the (new) astropy.units.physical.PhysicalType class instead of strings and the function astropy.units.physical.get_physical_type can now translate strings to these objects. [#11204]

    • The function astropy.units.physical.def_physical_type was created to either define entirely new physical types, or to add more physical type names to an existing physical types. [#11204]

    • PhysicalType's can be operated on using operations multiplication, division, and exponentiation are to facilitate dimensional analysis. [#11204]

    • It is now possible to define aliases for units using astropy.units.set_enabled_aliases. This can be used when reading files that have misspelled units. [#11258]

    • βž• Add a new "DN" unit, units.dn or units.DN, representing data number for a detector. [#11591]

    astropy.utils ^

    • Added ssl_context and allow_insecure options to download_file, as well as the ability to optionally use the certifi package to provide root CA certificates when downloading from sites secured with TLS/SSL. [#10434]

    • is publicly scoped (previously the private function _find_pkg_data_path) for obtaining file paths without checking if the file/directory exists, as long as the package and module do. [#11006]

    • πŸ—„ Deprecated astropy.utils.OrderedDescriptor and astropy.utils.OrderedDescriptorContainer, as new features in Python 3 make their use less compelling. [#11094, #11099]

    • astropy.utils.masked provides a new Masked class/factory that can be used to represent masked ndarray and all its subclasses, including Quantity and its subclasses. These classes can be used inside coordinates, but the mask is not yet exposed. Generally, the interface should be considered experimental. [#11127, #11792]

    • βž• Add new utils.parsing module to with helper wrappers around ply. [#11227]

    • πŸ”„ Change the Time and IERS leap second handling so that the leap second table is updated only when a Time transform involving UTC is performed. Previously this update check was done the first time a Time object was created, which in practice occured when importing common astropy subpackages like astropy.coordinates. Now you can prevent querying internet resources (for instance on a cluster) by setting iers.conf.auto_download = False. This can be done after importing astropy but prior to performing any Time scale transformations related to UTC. [#11638]

    • βž• Added a new module at astropy.utils.compat.optional_deps to consolidate the definition of HAS_x optional dependency flag variables, like HAS_SCIPY. [#11490]

    astropy.wcs ^

    • βž• Add IVOA UCD mappings for some FITS WCS keywords commonly used in solar physics. [#10965]

    • βž• Add STOKES FITS WCS keyword to the IVOA UCD mapping. [#11236]

    • ⚑️ Updated bundled version of WCSLIB to version 7.6. See for a list of included changes. [#11549]

    API Changes


    • For input to representations, subclasses of the class required for a given attribute will now be allowed in. [#11113]

    • Except for UnitSphericalRepresentation, shortcuts in representations now allow for attached differentials. [#11467]

    • πŸ‘ Allow coordinate name strings as input to SkyCoord.is_transformable_to. [#11552]


    • Change z_at_value to use scipy.optimize.minimize_scalar with default method Brent (other options Bounded and Golden) and accept bracket option to set initial search region. [#11080]

    • Clarified definition of inputs to angular_diameter_distance_z1z2. The function now emits AstropyUserWarning when z2 is less than z1. [#11197]

    • Split cosmology realizations from core classes, moving the former to new file realizations. [#11345]

    • Since cosmologies are immutable, the initialization signature and values can be stored, greatly simplifying cloning logic and extending it to user-defined cosmology classes that do not have attributes with the same name as each initialization argument. [#11515]

    • Cloning a cosmology with changed parameter(s) now appends "(modified)" to the new instance's name, unless a name is explicitly passed to clone. [#11536]

    • πŸ‘ Allow m_nu to be input as any quantity-like or array-like -- Quantity, array, float, str, etc. Input is passed to the Quantity constructor and converted to eV, still with the prior mass-energy equivalence enabled. [#11640] ^

    • For conversion between FITS tables and astropy Table, the standard mask values of NaN for float and null string for string are now properly recognized, leading to a MaskedColumn with appropriately set mask instead of a Column with those values exposed. Conversely, when writing an astropy Table to a FITS tables, masked values are now consistently converted to the standard FITS mask values of NaN for float and null string for string (i.e., not just for tables with masked=True, which no longer is guaranteed to signal the presence of MaskedColumn). [#11222]

    • πŸ—„ The use of version='1.0' is now fully deprecated in constructing a [#11659]

    astropy.modeling ^

    • βœ‚ Removed deprecated astropy.modeling.blackbody module. [#10972]

    astropy.table ^

    • βž• Added Column.value as an alias for the existing attribute. This makes accessing a column's underlying data array consistent with the .value attribute available for Time and Quantity objects. [#10962]

    • In reading from a FITS tables, the standard mask values of NaN for float and null string for string are properly recognized, leading to a MaskedColumn with appropriately set mask. [#11222]

    • πŸ”„ Changed the implementation of the table.index.Index class so instantiating from this class now returns an Index object as expected instead of a SlicedIndex object. [#11333]

    astropy.units ^

    • The physical_type attribute of units now returns an instance of astropy.units.physical.PhysicalType instead of a string. Because PhysicalType instances can be compared to strings, no code changes should be necessary when making comparisons. The string representations of different physical types will differ from previous releases. [#11204]

    • Calling Unit() with no argument now returns a dimensionless unit, as was documented but not implemented. [#11295]

    astropy.utils ^

    • βœ‚ Removed deprecated utils.misc.InheritDocstrings and utils.timer. [#10281]

    • βœ‚ Removed usage of deprecated ipython stream in utils.console. [#10942]

    astropy.wcs ^

    • πŸ—„ Deprecate accuracy argument in all_world2pix which was mistakenly documented, in the case accuracy was ever used. [#11055]

    πŸ› Bug Fixes


    • πŸ›  Fixes for convolve_fft documentation examples. [#11510]


    • πŸ‘ Allow Distance instances with negative distance values as input for SphericalRepresentation. This was always noted as allowed in an exception message when a negative Quantity with length units was passed in, but was not actually possible to do. [#11113]

    • πŸ‘‰ Makes the Angle.to_string method to follow the format described in the docstring with up to 8 significant decimals instead of 4. [#11153]

    • Ensure that proper motions can be calculated when converting a SkyCoord with cartesian representation to unit-spherical, by fixing the conversion of CartesianDifferential to UnitSphericalDifferential. [#11469]

    • When re-representing coordinates from spherical to unit-spherical and vice versa, the type of differential will now be preserved. For instance, if only a radial velocity was present, that will remain the case (previously, a zero proper motion component was added). [#11482]

    • ⚠ Ensure that wrapping of Angle does not raise a warning even if nan are present. Also try to make sure that the result is within the wrapped range even in the presence of rounding errors. [#11568]

    • Comparing a non-SkyCoord object to a SkyCoord using == no longer raises an error. [#11666]

    • Different SkyOffsetFrame classes no longer interfere with each other, causing difficult to debug problems with the origin attribute. The origin attribute now no longer is propagated, so while it remains available on a SkyCoord that is an offset, it no longer is available once that coordinate is transformed to another frame. [#11730] [#11730]


    • Cosmology instance names are now immutable. [#11535] ^

    • πŸ›  Fixed bug where writing a table that has comments defined (via tbl.meta['comments']) with the 'csv' format was failing. Since the formally defined CSV format does not support comments, the comments are now just ignored unless comment=<comment prefix> is supplied to the write() call. [#11475]

    • πŸ›  Fixed the issue where the CDS reader failed to treat columns as nullable if the ReadMe file contains a limits specifier. [#11531]

    • Made sure that the CDS reader does not ignore an order specifier that may be present after the null specifier '?'. Also made sure that it checks null values only when an '=' symbol is present and reads description text even if there is no whitespace after '?'. [#11593] ^

    • Fix ColDefs.add_col/del_col to allow in-place addition or removal of a column. [#11338]

    • πŸ›  Fix indexing of fits.Header with Numpy integers. [#11387]

    • 0️⃣ Do not delete EXTNAME for compressed image header if a default and non-default EXTNAME are present. [#11396]

    • ⚠ Prevent warnings about HIERARCH with CompImageHeader class. [#11404]

    • πŸ›  Fixed regression introduced in Astropy 4.0.5 and 4.2.1 with verification of FITS headers with HISTORY or COMMENT cards with long (> 72 characters) values. [#11487]

    • πŸ›  Fix reading variable-length arrays when there is a gap between the data and the heap. [#11688]

    • NumericArray converter now properly broadcasts scalar mask to array. [#11157]

    • VOTables are now written with the correct namespace and schema location attributes. [#11659]

    astropy.modeling ^

    • πŸ›  Fixes the improper propagation of bounding_box from astropy.modeling.models to their inverses. For cases in which the inverses bounding_box can be determined, the proper calculation has been implemented. [#11414]

    • πŸ›  Bugfix to allow rotation models to accept arbitrarily-shaped inputs. [#11435]

    • πŸ›  Bugfixes for astropy.modeling to allow fix_inputs to accept empty dictionaries and dictionaries with numpy integer keys. [#11443]

    • πŸ›  Bugfix for how SPECIAL_OPERATORS are handled. [#11512]

    • πŸ›  Fixes Model crashes when some inputs are scalars and during some types of output reshaping. [#11548]

    • πŸ›  Fixed bug in LevMarLSQFitter when using weights and vector inputs. [#11603]

    astropy.stats ^

    • πŸ›  Fixed a bug with the copy=False option when carrying out sigma clipping - previously if masked=False this still copied the data, but this will now change the array in-place. [#11219]

    astropy.table ^

    • Ensure that adding a Quantity or other mixin column to a Table does not have side effects, such as creating an associated info instance (which would lead to slow-down of, e.g., slicing afterwards). [#11077]

    • When writing to a FITS tables, masked values are again always converted to the standard FITS mask values of NaN for float and null string for string, not just for table with masked=True. [#11222]

    • Using Table.to_pandas() on an indexed Table with masked integer values now correctly construct the pandas.DataFrame. [#11432]

    • πŸ›  Fixed Table HTML representation in Jupyter notebooks so that it is horizontally scrollable within Visual Studio Code. This was done by wrapping the <table> in a <div> element. [#11476]

    • πŸ›  Fix a bug where a string-valued Column that happened to have a unit attribute could not be added to a QTable. Such columns are now simply kept as Column instances (with a warning). [#11585]

    • πŸ›  Fix an issue in Table.to_pandas(index=<colname>) where the index column name was not being set properly for the DataFrame index. This was introduced by an API change in pandas version 1.3.0. Previously when creating a DataFrame with the index set to an astropy Column, the DataFrame index name was automatically set to the column name. [#11921]

    astropy.time ^

    • πŸ›  Fix a thread-safety issue with initialization of the leap-second table (which is only an issue when ERFA's built-in table is out of date). [#11234]

    • πŸ›  Fixed converting a zero-length time object from UTC to UT1 when an empty array is passed. [#11516]


    • Distribution instances can now be used as input to Quantity to initialize QuantityDistribution. Hence, distribution * unit and distribution << unit will work too. [#11210]

    astropy.units ^

    • 🚚 Move non-astronomy units from to a new file. [#11142]

    • The physical type of astropy.units.mol / astropy.units.m ** 3 is now defined as molar concentration. It was previously incorrectly defined as molar volume. [#11204]

    • πŸ‘‰ Make ufunc helper lookup thread-safe. [#11226]

    • πŸ“œ Make Unit string parsing (as well as Angle parsing) thread-safe. [#11227]

    • Decorator astropy.units.decorators.quantity_input now only evaluates return type annotations based on UnitBase or FunctionUnitBase types. Other annotations are skipped over and are not attempted to convert to the correct type. [#11506]

    astropy.utils ^

    • πŸ‘‰ Make lazyproperty and classdecorator thread-safe. This should fix a number of thread safety issues. [#11224]


    • πŸ›  Fixed a bug that resulted in some parts of grid lines being visible when they should have been hidden. [#11380]

    • πŸ›  Fixed a bug that resulted in time_support() failing for intervals of a few months if one of the ticks was the month December. [#11615]

    astropy.wcs ^

    • fit_wcs_from_points now produces a WCS with integer NAXIXn values. [#10865]

    • ⚑️ Updated bundled version of WCSLIB to v7.4, fixing a bug that caused the coefficients of the TPD distortion function to not be written to the header. [#11260]

    • πŸ›  Fixed a bug in assigning type when converting colsel to numpy.ndarray. [#11431]

    • βž• Added WCSCOMPARE_* constants to the list of WCSLIB constants available/exposed through the astropy.wcs module. [#11647]

    • πŸ›  Fix a bug that caused APE 14 WCS transformations for FITS WCS with ZOPT, BETA, VELO, VOPT, or VRAD CTYPE to not work correctly. [#11781]

    Other Changes and Additions

    • πŸ”§ The configuration file is no longer created by default when importing astropy and its existence is no longer required. Affiliated packages should update their module to remove the block using update_default_config and ConfigurationDefaultMissingWarning. [#10877]

    • πŸ“‡ Replace pkg_resources (from setuptools) with importlib.metadata which comes from the stdlib, except for Python 3.7 where the backport package is added as a new dependency. [#11091]

    • Turn on numpydoc's numpydoc_xref_param_type to create cross-references for the parameter types in the Parameters, Other Parameters, Returns and Yields sections of the docstrings. [#11118]

    • πŸ“„ Docstrings across the package are standardized to enable references. Also added is an Astropy glossary-of-terms to define standard inputs, e.g. quantity-like indicates an input that can be interpreted by astropy.units.Quantity. [#11118]

    • 🐧 Binary wheels are now built to the manylinux2010 specification. These wheels should be supported on all versions of pip shipped with Python 3.7+. [#11377]

    • 0️⃣ The name of the default branch for the astropy git repository has been renamed to main, and the documentation and tooling has been updated accordingly. If you have made a local clone you may wish to update it following the instructions in the repository's README. [#11379]

    • Sphinx cross-reference link targets are added for every PhysicalType. Now in the parameter types in the Parameters, Other Parameters, Returns and Yields sections of the docstring, the physical type of a quantity can be annotated in square brackets. E.g. distance : `~astropy.units.Quantity` ['length'] [#11595]

    • πŸ‘ The minimum supported version of ipython is now 4.2. [#10942]

    • πŸ‘ The minimum supported version of pyerfa is now 1.7.3. [#11637]