cf.Field.__getitem__

Field.__getitem__(indices)

Return a subspace of the field defined by metadata values

Subspacing by axis indices uses an extended Python slicing syntax, which is similar to numpy array indexing:

>>> f.shape
(12, 73, 96)
>>> f[...].shape
(12, 73, 96)
>>> f[slice(0, 12), :, 10:0:-2].shape
(12, 73, 5)
>>> f[..., f.coord('longitude')<180].shape
(12, 73, 48)

There are three extensions to the numpy indexing functionality:

• Size 1 axes are never removed.

  An integer index i takes the i-th element but does not reduce the rank of the output array by one:

  >>> f.shape
  (12, 73, 96)
  >>> f[0].shape
  (1, 73, 96)
  >>> f[3, slice(10, 0, -2), 95:93:-1].shape
  (1, 5, 2)
  

• The indices for each axis work independently.

  When more than one axis’s slice is a 1-d boolean sequence or 1-d sequence of integers, then these indices work independently along each axis (similar to the way vector subscripts work in Fortran), rather than by their elements:

  >>> f.shape
  (12, 73, 96)
  >>> f[:, [0, 72], [5, 4, 3]].shape
  (12, 2, 3)
  

  Note that the indices of the last example would raise an error when given to a numpy array.

• Boolean indices may be any object which exposes the numpy array interface, such as the field’s coordinate objects:

  >>> f[:, f.coord('latitude')<0].shape
  (12, 36, 96)
  

f.__getitem__(indices) <==> f[indices]

New in version 2.0.

Examples 1:

>>> g = f[..., 0, :6, 9:1:-2, [1, 3, 4]]

Returns:out: cf.{+Variable}