# cf.FieldAncillary.period¶

FieldAncillary.period(*value)[source]

Return or set the period of the data.

This is distinct from the cyclicity of individual axes.

Parameters
value: optional

The period. The absolute value is used. May be set to any numeric scalar object, including numpy and Data objects. The units of the radius are assumed to be the same as the data, unless specified by a Data object.

If value is None then any existing period is removed from the construct.

Returns
Data or None

The period prior to the change, or the current period if no value was specified. None is always returned if the period had not been set previously.

Examples:

>>> print(c.period())
None
>>> c.Units
<Units: degrees_east>
>>> print(c.period(360))
None
>>> c.period()
<CF Data(): 360.0 'degrees_east'>
>>> import math
>>> c.period(cf.Data(2*math.pi, 'radians'))
<CF Data(): 360.0 degrees_east>
>>> c.period()
<CF Data(): 6.28318530718 radians>
>>> c.period(None)
<CF Data:() 6.28318530718 radians>
>>> print(c.period())
None
>>> print(c.period(-360))
None
>>> c.period()
<CF Data(): 360.0 degrees_east>