# cf.Datum¶

class cf.Datum(parameters=None, source=None, copy=True)[source]

Bases: cfdm.datum.Datum

A datum component of a coordinate reference construct of the CF data model.

A datum is a complete or partial definition of the zeroes of the dimension and auxiliary coordinate constructs which define a coordinate system.

The datum may contain the definition of a geophysical surface which corresponds to the zero of a vertical coordinate construct, and this may be required for both horizontal and vertical coordinate systems.

Elements of the datum not specified may be implied by the properties of the dimension and auxiliary coordinate constructs referenced by the cf.CoordinateReference instance that contains the datum.

New in version 3.0.0.

Initialisation

Parameters
parameters: dict, optional

Set parameters. The dictionary keys are parameter names, with corresponding values. Ignored if the source parameter is set.

Parameters may also be set after initialisation with the set_parameters and set_parameter methods.

Parameter example:

parameters={'earth_radius': 6371007.}

source: optional

Initialise the parameters from those of source.

Note that if source is a Datum instance then cf.Datum(source=source) is equivalent to source.copy().

copy: bool, optional

If False then do not deep copy input parameters prior to initialisation. By default arguments are deep copied.

## Parameters¶

Methods

 clear_parameters Remove all parameters. del_parameter Delete a parameter. get_parameter Get a parameter value. has_parameter Whether a parameter has been set. parameters Return all parameters. set_parameter Set a parameter-valued term. set_parameters Set parameters.

## NetCDF¶

Methods

 nc_del_variable Remove the netCDF variable name. nc_get_variable Return the netCDF variable name. nc_has_variable Whether the netCDF variable name has been set. nc_set_variable Set the netCDF variable name.

## Miscellaneous¶

Methods

 copy Return a deep copy. equals Whether two instances are the same.

### Groups¶

Methods

 nc_variable_groups Return the netCDF variable group hierarchy. nc_set_variable_groups Set the netCDF variable group hierarchy. nc_clear_variable_groups Remove the netCDF variable group hierarchy.

## Special¶

Methods

 __bool__ Called by the bool built-in function. __deepcopy__ Called by the copy.deepcopy function. cf.Datum.__nonzero__ __repr__ Called by the repr built-in function. __str__ Called by the str built-in function.