Change log

version 3.0.0 (first Python 3 version)


  • Complete refactor for Python 3, including some API changes.

    Scripts written for version 2.x but running under version 3.x should either work as expected, or provide informative error mesages on the new API usage. However, it is advised that the outputs of older scripts be checked when running with Python 3 versions of the cf library.

version 2.3.5 (last Python 2 version)


  • Changed calculation of chunksize in parallel case to avoid potential problems and introduced a new method cf.SET_PERFORMANCE to tune the chunksize and the fraction of memory to keep free.

version 2.3.4


  • Fix bug in creating a during cell method during a field collapse.

version 2.3.3


  • Allow failure to compile to go through with a warning, rather than failing to install. if this happens, reading a PP/UM file will result in “Exception: Can’t determine format of file test2.pp”
  • Fixed bug in Field.convolution_filter giving false error over units.

version 2.3.2


  • cf.Field.regridc now compares the units of the source and destination grids and converts between them if possible or raises an error if they are not equivalent.

version 2.3.1


  • Fixed bug in cf.Field.regridc that caused it to fail when regridding a multidimensional field along only one dimension.
  • Fixed bug which in which the default logarithm is base 10, rather than base e

version 2.3.0


  • The collapse method can now be parallelised by running any cf-python script with mpirun if mpi4py is installed. This is an experimental feature and is not recommended for operational use. None of the parallel code is executed when a script is run in serial.

version 2.2.8


  • Bug fix: better handle subspacing by multiple multidimensional items

version 2.2.7


  • Bug fix: correctly set units of bounds when the Data object inserted with insert_bounds has units of ‘’. In this case the bounds of the parent coordinate are now inherited.

version 2.2.6


  • Improved error messages
  • Changed behaviour when printing reference times with a calendar of “none” - no longer attemps a to create a date-time representation

version 2.2.5


  • Fixed bug with HDF chunk sizes that prevented the writing of large files

version 2.2.4


  • Interim fix for with HDF chunk sizes that prevented the writing of large files

version 2.2.3


  • During writing, disallow the creation of netCDF variable names that contain characters other than letters, digits, and underscores.

version 2.2.3


  • During writing, disallow the creation of netCDF variable names that contain characters other than letters, digits, and underscores.

version 2.2.2


  • Fix for removing duplicated netCDF dimensions when writing data on (e.g.) tripolar grids.

version 2.2.1


  • Fix for calculating are weights from projection coordinates

version 2.2.0


  • Updated for netCDF4 v1.4 cftime API changes

Version 2.1.9 - 31 May 2018

  • Allowed invalid units through. Can test with cf.Units.isvalid.

Version 2.1.8 - 08 March 2018

  • Fixed bug when weights parameter is a string in Field.collapse

Version 2.1.7 - 13 February 2018

  • Fixed bug in Field.collapse when doing climatological time collapse with only one persiod per year/day

Version 2.1.6 - 09 February 2018

  • Fixed bug in Variable.mask

Version 2.1.4 - 09 February 2018

  • Added override_calendar method to coordinates and domain ancillaries that changes the calendar of the bounds, too
  • Fixed bug in cf.Data.where when the condition is a cf.Query object (f5e0d43)
  • Fixed bug in Variable.mask

Version 2.1.3 - 07 February 2018

  • Allowed scipy and matplotlib imorts to be optional (23a4347)

Version 2.1.2 - 28 November 2017

  • Added group_span and contiguous_group options to Field.collapse

Version 2.1.1 - 10 November 2017

  • Dissallowed raising offset units to a power (e.g. taking the square of data in units of K @ 273.15).
  • Removed len() of Field (previously always, and misleadingly, returned 1)
  • Fixed setting of cell methods after climatological time collapses
  • Added printing of ncvar in Field.__str__ and Field.dump
  • Added user stash table option to cfa script

Version 2.1 - 30 October 2017

  • Misc. bug fixes

Version 2.0.6 - 28 September 2017

  • Removed error when finds no fields - an empty field list is now returned
  • Allowed the count method on a field (it was only on a data object before)

Version 2.0.5 - 19 September 2017

  • Bug fix when creating wrap-around subspaces from cyclic fields
  • Fix (partial?) for memory leak when reading UM PP and fields files

Version 2.0.4 - 15 September 2017

  • submodel property for PP files
  • API change for cf.Field.axis: now returns a cf.DomainAxis object by default
  • Bug fix in cf.Field.where
  • Bug fix when initializing a field with the source parameter
  • Changed default ouptut format to NETCDF4 (from NETCDF3_CLASSIC)

Vesion 2.0.1.post1 - 12 July 2017

  • Bug fix for reading DSG ragged arrays

Vesion 2.0.1 - 11 July 2017

Vesion 2.0 - 07 July 2017

  • First release with full CF data model and full CF-1.6 compliance (including DSG)

Version 1.5.4.post4 - 07 July 2017

Version 1.5.4.post1 - 13 June 2017

  • removed errant scikit import

Version 1.5.4 - 09 June 2017

  • Tripolar regridding

Version 1.5.3 -

  • Updated STASH code to standard_name table (with thanks to Jeff Cole)
  • Fixed bug when comparing masked arrays for equality

Version 1.5.2 - 17 March 2017

  • Fixed bug when accessing PP file whose format/endian/word-size has been specified

Version 1.5.1 - 14 March 2017

  • Can specify ‘pp’ or ‘PP’ in um option to

Version 1.5 - 24 February 2017

  • Changed weights in calculation of variance to reliability weights (from frequency weights). This not only scientifically better, but faster, too.

Version 1.4 - 22 February 2017

  • Rounded datetime to time-since conversions to the nearest microsecond, to reflect the accuracy of netCDF4.netcdftime
  • Removed import tests from
  • New option –um to cfa, cfdump
  • New parameter um to

Version 1.3.3 - 31 January 2017

  • Rounded datetime to time-since conversions to the nearest microsecond, to reflect the accuracy of netCDF4.netcdftime
  • Fix for netCDF4.__version__ > 1.2.4 do to with datetime.calendar handle with care

Version 1.3.2 - 21 September 2016

  • Added –build-id to LDFLAGS in umread Makefile, for sake of RPM builds (otherwise fails when building debuginfo RPM). Pull request #16, thanks to Klaus Zimmerman.
  • Improved test handling. Pull request #21, thanks to Klaus Zimmerman.
  • Removed udunits2 database. This removes the modified version of the udunits2 database in order to avoid redundancies, possible version incompatibilities, and license questions. The modifications are instead carried out programmatically in Pull request #20, thanks to Klaus Zimmerman.

Version 1.3.1 - 09 September 2016

  • New method: cf.Field.unlimited, and new ‘unlimited’ parameter to cf.write and cfa

Version 1.3 - 05 September 2016

  • Removed asreftime, asdatetime and dtvarray methods
  • New method: convert_reference_time for converting reference time data values to have new units.

Version 1.2.3 - 23 August 2016

  • Fixed bug in Data.equals

Version 1.2.2 - 22 August 2016

  • Fixed bug in binary operations to do with the setting of Partition.part
  • Added TimeDuration functionality to get_bounds cellsizes parameter. Also new parameter flt (“fraction less than”) to position the coordinate within the cell.

Version 1.2 - 05 July 2016

  • Added HDF_chunks methods

Version 1.1.11 - 01 July 2016

  • Added cellsize option to cf.Coordinate.get_bounds, and fixed bugs
  • Added variable_attributes option to cf.write
  • Added cf.ENVIRONMENT method

Version 1.1.10 - 23 June 2016

  • Added reference_datetime option to cf.write
  • Fixed bug in which incorrectly ordered vertical coordinates

Version 1.1.9 - 17 June 2016

  • New methods cf.Variable.files and cf.Data.files, cf.Field.files which report which files are referenced by the data array.
  • Fix to stop partitions return numpy.bool_ instead of numpy.ndarray
  • Fix to determining cyclicity of regridded fields.
  • Functionality to recursively read directories in, cfa and cfump
  • Print warning but carry on when ESMF import fails
  • Fixed bug in cf.Field.subspace when accessing axes derived from UM format files

Version 1.1.8 - 18 May 2016

  • Slightly changed the compression API to cf.write
  • Added compression support to the cfa command line script
  • Added functionality to change data type on writing to cf.write and cfa - both in general and for with extra convienience for the common case of double to single (and vice versa).
  • Removed annoying debug print statements from

Version 1.1.7 - 04 May 2016

  • Added fix for change in numpy behaviour (numpy.number types do not support assingment)
  • Added capability to load in a user STASH to standard name table:

Version 1.1.6 - 27 April 2016

  • Added –reference_datetime option to cfa
  • Bug fix to cf.Field.collapse when providing cf.Query objects via the group parameter
  • Added auto regridding method, which is now the default

Version 1.1.5 - 03 March 2016

  • Bug fix in cf.Field.where when using cf.masked
  • conda installation (with thanks to Andy Heaps)
  • Bug fix for type casting in cf.Field.collapse
  • Dispay long_name if it exists and there is no standard_name
  • Fix for compiling the UM C code on certiain OSs (with thanks to Simon Wilson)
  • Fixed incorrect assignment of cyclicity in cf.Field.regrids
  • Nearest neighbour regridding in cf.Field.regrids

Version 1.1.4 - 09 February 2016

  • Bug fix to cf.Field.autocyclic
  • Bug fix to cf.Field.clip - now works when limit units are supplied
  • New methods: cf.Data.round, cf.Field.Round
  • Added lbtim as a Field property when reading UM files
  • Fixed coordinate creation for UM atmosphere_hybrid_height_coordinate
  • Bug fix to handling of cyclic fields by cf.Field.regrids
  • Added nearest neighbour field regridding
  • Changed keyword ignore_dst_mask in cf.Field.regrids to use_dst_mask, which is false by default

Version 1.1.3 - 10 December 2015

  • Bug fixes to cf.Field.collapse when the “group” parameter is used
  • Correct setting of cyclic axes on regridded fields
  • Updates to STASH_to_CF.txt table: 3209, 3210

Version 1.1.2 - 01 December 2015

  • Updates to STASH_to_CF.txt table
  • Fixed bug in decoding UM version in
  • Fixed bug in cf.units.Utime.num2date
  • Fixed go-slow behaviour for silly BZX, BDX in PP and fields file lookup headers

Version 1.1.1 - 05 November 2015

  • Fixed bug in decoding UM version in

Version 1.1 - 28 October 2015

  • Fixed bug in cf.Units.conform
  • Changed cf.Field.__init__ so that it works with just a data object
  • Added cf.Field.regrids for lat-lon regridding using ESMF library
  • Removed support for netCDF4-python versions < 1.1.1
  • Fixed bug which made certain types of coordinate bounds non-contiguous after transpose
  • Fixed bug with i=True in cf.Field.where and in cf.Field.mask_invalid
  • cyclic methods now return a set, rather than a list
  • Fixed bug in _write_attributes which might have slowed down some writes to netCDF files.
  • Reduced annoying redirection in the documentation
  • Added cf.Field.field method and added top_level keyword to
  • Fixed bug in calculation of standard deviation and variance (the bug caused occasional crashes - no incorrect results were calculated)
  • In items method (and friends), removed strict_axes keyword and added axes_all, axes_superset and axes_subset keywords

Version 1.0.3 - 23 June 2015

  • Added default keyword to fill_value() and fixed bugs when doing delattr on _fillValue and missinge_value properties.

Version 1.0.2 - 05 June 2015

  • PyPI release

Version 1.0.1 - 01 June 2015

  • Fixed bug in when using the select keyword to

Version 1.0 - 27 May 2015

  • Max OS support
  • Limited Nd funtionality to Field.indices
  • Correct treatment of add_offset and scale_factor
  • Replaced -a with -x in cfa and cfdump scripts
  • added ncvar_identities parameter to cf.aggregate
  • Performance improvements to field subspacing
  • Documentation
  • Improved API to match, select, items, axes, etc.
  • Reads UM fields files
  • Optimised readin PP and UM fields files
  • cf.collapse replaced by cf.Field.collapse
  • cf.Field.collapse includes CF climatological time statistics

Version - 09 January 2015

  • Fixed bug for changes to netCDF4-python library versions >= 1.1.2
  • Miscellaneous bug fixes

Version 0.9.9 - 05 January 2015

  • Added netCDF4 compression options to cf.write.
  • Added __mod__, __imod__, __rmod__, ceil, floor, trunc, rint methods to cf.Data and cf.Variable
  • Added ceil, floor, trunc, rint to cf.Data and cf.Variable
  • Fixed bug in which array cf.Data.array sometimes behaved like cf.Data.varray
  • Fixed bug in which affected reading fields with formula_terms.
  • Refactored the test suite to use the unittest package
  • Cyclic axes functionality
  • Documentation updates

Version - 14 July 2014

  • Implemented multiple grid_mappings (CF trac ticket #70)
  • Improved functionality and speed of field aggregation and cfa``a and ``cfdump command line utilities.
  • Collapse methods on cf.Data object (min, max, mean, var, sd, sum, range, mid_range).
  • Improved match/select functionality

Version - 13 March 2014

  • Copes with PP fields with 365_day calendars
  • Revamped CFA files in line with the evolving standard. CFA files from PP data created with a previous version will no longer work.

Version - December 2013

Version 0.9.8 - 06 December 2013

  • Improved API.
  • Plenty of speed and memory optimizations.
  • A proper treatment of datetimes.
  • WGDOS-packed PP fields are now unpacked on demand.
  • Fixed bug in for numpy v1.7. Fixed bug when deleting the ‘id’ attribute.
  • Assign a standard name to aggregated PP fields after aggregation rather than before (because some stash codes are too similar, e.g. 407 and 408).
  • New subclasses of cf.Coordinate: cf.DimensionCoordinate and cf.AuxiliaryCoordinate.
  • A cf.Units object is now immutable.

Version - 26 April 2013

  • Fixed endian bug in CFA-netCDF files referring to PP files
  • Changed default output format to NETCDF3_CLASSIC and trap error when when writing unsigned integer types and the 64-bit integer type to file formats other than NETCDF4.
  • Changed unhelpful history created when aggregating

Version 0.9.7 - 24 April 2013

  • Read and write CFA-netCDF files
  • Field creation interface
  • New command line utilities: cfa, cfdump
  • Redesigned repr, str and dump() output (which is shared with cfa and cfdump)
  • Removed superceded (by cfa) command line utilities pp2cf, cf2cf
  • Renamed the ‘subset’ method to ‘select’
  • Now needs netCDF4-python 0.9.7 or later (and numpy 1.6 or later)

Version - 27 March 2013

  • Fixed bug in cf/ which caused the creation of incorrect latitude coordinate arrays.

Version - 20 February 2013

  • Fixed bug in cf/ which caused a failure when a file with badly formatted units was encountered.

Version 0.9.6 - 27 November 2012

  • Assignment to a field’s data array with metadata-aware broadcasting, assigning to subspaces, assignment where data meets conditions, assignment to unmasked elements, etc. (setitem method)
  • Proper treatment of the missing data mask, including metadata-aware assignment (setmask method)
  • Proper treatment of ancillary data.
  • Ancillary data and transforms are subspaced with their parent field.
  • Much faster aggregation algorithm (with thanks to Jonathan Gregory). Also aggregates fields transforms, ancillary variables and flags.

Version 0.9.5 - 01 October 2012

  • Restructured documentation and package code files.
  • Large Amounts of Massive Arrays (LAMA) functionality.
  • Metadata-aware field manipulation and combination with metadata-aware broadcasting.
  • Better treatment of cell measures.
  • Slightly faster aggregation algorithm (a much improved one is in development).
  • API changes for clarity.
  • Bug fixes.
  • Added ‘TEMPDIR’ to the cf.CONSTANTS dictionary
  • This is a snapshot of the trunk at revision r195.

Version - 19 September 2012

  • Loads of exciting improvements - mainly LAMA functionality, metadata-aware field manipulation and documentation.
  • This is a snapshot of the trunk at revision r185. A proper vn0.9.5 release is imminent.

Version - 17 April 2012

  • General bug fixes and code restructure

Version 0.9.4 - 15 March 2012

  • A proper treatment of units using the Udunits C library and the extra time functionality provided by the netCDF4 package.
  • A command line script to do CF-netCDF to CF-netCDF via cf-python.

Version - 08 February 2012

  • Objects renamed in line with the CF data model: ‘Space’ becomes ‘Field’ and ‘Grid’ becomes ‘Space’.
  • Field aggregation using the CF aggregation rules is available when reading fields from disk and on fields in memory. The data of a field resulting from aggregation are stored as a collection of the data from the component fields and so, as before, may be file pointers, arrays in memory or a mixture of these two forms.
  • Units, missing data flags, dimension order, dimension direction and packing flags may all be different between data components and are conformed at the time of data access.
  • Files in UK Met Office PP format may now be read into CF fields.
  • A command line script for PP to CF-netCDF file conversion is provided.

Version 0.9.3 - 05 January 2012

  • A more consistent treatment of spaces and lists of spaces (Space and SpaceList objects respectively).
  • A corrected treatment of scalar or 1-d, size 1 dimensions in the space and its grid.
  • Data stored in Data objects which contain metadata need to correctly interpret and manipulate the data. This will be particularly useful when data arrays spanning many files/arrays is implemented

Version 0.9.2 - 26 August 2011

  • Created a script for easier installation (with thanks to Jeff Whitaker).
  • Added support for reading OPeNDAP-hosted datasets given by URLs.
  • Restructured the documentation.
  • Created a test directory with scripts and sample output.
  • No longer fails for unknown calendar types (such as ‘360d’).

version 0.9.1


  • First release.