The cf.FieldList object

A cf.FieldList is an ordered sequence of cf.Field objects.

List-like operators

It supports all of the python list-like operations. For example:

>>> fl
[<CF Field: x_wind(grid_latitude(110), grid_longitude(106)) m s-1>,
 <CF Field: air_temperature(time(12), latitude(73), longitude(96)) K>]
>>> fl[0]
<CF Field: air_temperature(time(12), latitude(73), longitude(96)) K>
>>> fl[::-1]
[<CF Field: air_temperature(time(12), latitude(73), longitude(96)) K>,
 <CF Field: x_wind(grid_latitude(110), grid_longitude(106)) m s-1>]
>>> fl[slice(1, -1, 2)]
[<CF Field: x_wind(grid_latitude(110), grid_longitude(106)) m s-1>]

Note that an indexing by an integer returns an individual field, but other types of index always return a field list.

>>> len(fl)
2
>>> f = fl.pop()
>>> f
<CF Field: air_temperature(time(12), latitude(73), longitude(96)) K>
>>> len(fl)
1
>>> fl.append(f.copy())
>>> len(fl)
2
>>> f in fl
True
>>> fl
[<CF Field: x_wind(grid_latitude(110), grid_longitude(106)) m s-1>,
 <CF Field: air_temperature(time(12), latitude(73), longitude(96)) K>]
>>> fl.reverse()
[<CF Field: air_temperature(time(12), latitude(73), longitude(96)) K>,
 <CF Field: x_wind(grid_latitude(110), grid_longitude(106)) m s-1>]
>>> fl += fl[-1].copy()
[<CF Field: x_wind(grid_latitude(110), grid_longitude(106)) m s-1>,
 <CF Field: air_temperature(time(12), latitude(73), longitude(96)) K>,
 <CF Field: x_wind(grid_latitude(110), grid_longitude(106)) m s-1>]

Selecting fields

One or more fields from a field list may be selected with the select method that returns a new field list containing the selected fields:

>>> fl
[<CF Field: x_wind(grid_latitude(110), grid_longitude(106)) m s-1>,
 <CF Field: air_temperature(time(12), latitude(73), longitude(96)) K>]
>>> fl.select('air_temperature')
<CF Field: air_temperature(time(12), latitude(73), longitude(96)) K>]
>>> fl.select('[air_temperature|x_wind]')
[<CF Field: x_wind(grid_latitude(110), grid_longitude(106)) m s-1>,
 <CF Field: air_temperature(time(12), latitude(73), longitude(96)) K>]
>>> fl.select('NOTHING')
[]

Manipulating the fields

For in-place changes, a for loop may be used to process each field element. For example to reverse the data array axis order of each field in-place:

>>> fl
[<CF Field: x_wind(grid_latitude(110), grid_longitude(106)) m s-1>,
 <CF Field: air_temperature(time(12), latitude(73), longitude(96)) K>]
>>> for f in fl:
...     f.transpose(i=True)
...
>>> fl
[<CF Field: x_wind(grid_longitude(106), grid_latitude(110)) m s-1>,
 <CF Field: air_temperature( longitude(96), latitude(73), time(12)) K>]

In-place changes to the fields may also be done with a list comprehension:

>>> [f.transpose(i=True) for f in fl]

For changes which result in new fields, a for loop or list comprehension may be used:

>>> new_fl = cf.FieldList([f.round() for f in fl])
>>> new_fl = cf.FieldList()
>>> for f in fl:
...     new_fl.append(f[0:3])
...
>>> new_fl
[<CF Field: x_wind(grid_longitude(3), grid_latitude(110)) m s-1>,
 <CF Field: air_temperature( longitude(3), latitude(73), time(12)) K>]

Sorting the fields

The field list may be sorted in-place with the sort method, that works in a similar way to the sort method of a built-in list. The only difference is that by default the fields are sorted by their identities (e.g their standard names). For example:

>>> fl
[<CF Field: eastward_wind(time(3), air_pressure(5), grid_latitude(110), grid_longitude(106)) m s-1>,
 <CF Field: ocean_meridional_overturning_streamfunction(time(12), region(4), depth(40), latitude(180)) m3 s-1>,
 <CF Field: air_temperature(time(12), latitude(64), longitude(128)) K>,
 <CF Field: eastward_wind(time(3), air_pressure(5), grid_latitude(110), grid_longitude(106)) m s-1>]
>>> fl.sort()
>>> fl
[<CF Field: air_temperature(time(12), latitude(64), longitude(128)) K>,
 <CF Field: eastward_wind(time(3), air_pressure(5), grid_latitude(110), grid_longitude(106)) m s-1>,
 <CF Field: eastward_wind(time(3), air_pressure(5), grid_latitude(110), grid_longitude(106)) m s-1>,
 <CF Field: ocean_meridional_overturning_streamfunction(time(12), region(4), depth(40), latitude(180)) m3 s-1>]
>>> fl.sort(reverse=True)
>>> fl
[<CF Field: ocean_meridional_overturning_streamfunction(time(12), region(4), depth(40), latitude(180)) m3 s-1>,
 <CF Field: eastward_wind(time(3), air_pressure(5), grid_latitude(110), grid_longitude(106)) m s-1>,
 <CF Field: eastward_wind(time(3), air_pressure(5), grid_latitude(110), grid_longitude(106)) m s-1>,
 <CF Field: air_temperature(time(12), latitude(64), longitude(128)) K>]