Merge pull request #215 from nipy/enh/reenable-parallelization-apply-214

ENH: Serialize+parallelize 4D ``apply()`` into 3D+t and add 'low memory' loading

nitransforms/base.py

@@ -7,6 +7,7 @@
 #
 ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
 """Common interface for transforms."""
+
 from pathlib import Path
 import numpy as np
 import h5py
@@ -146,13 +147,13 @@ def from_arrays(cls, coordinates, triangles):
  darrays = [
  nb.gifti.GiftiDataArray(
  coordinates.astype(np.float32),
- intent=nb.nifti1.intent_codes['NIFTI_INTENT_POINTSET'],
- datatype=nb.nifti1.data_type_codes['NIFTI_TYPE_FLOAT32'],
+ intent=nb.nifti1.intent_codes["NIFTI_INTENT_POINTSET"],
+ datatype=nb.nifti1.data_type_codes["NIFTI_TYPE_FLOAT32"],
  ),
  nb.gifti.GiftiDataArray(
  triangles.astype(np.int32),
- intent=nb.nifti1.intent_codes['NIFTI_INTENT_TRIANGLE'],
- datatype=nb.nifti1.data_type_codes['NIFTI_TYPE_INT32'],
+ intent=nb.nifti1.intent_codes["NIFTI_INTENT_TRIANGLE"],
+ datatype=nb.nifti1.data_type_codes["NIFTI_TYPE_INT32"],
  ),
  ]
  gii = nb.gifti.GiftiImage(darrays=darrays)
@@ -279,6 +280,22 @@ def __add__(self, b):
 
  return TransformChain(transforms=[self, b])
 
+ def __len__(self):
+ """
+ Enable ``len()``.
+
+ By default, all transforms are of length one.
+ This must be overriden by transforms arrays and chains.
+
+ Example
+ -------
+ >>> T1 = TransformBase()
+ >>> len(T1)
+ 1
+
+ """
+ return 1
+
  @property
  def reference(self):
  """Access a reference space where data will be resampled onto."""
@@ -335,10 +352,8 @@ def apply(self, *args, **kwargs):
 
  Deprecated. Please use ``nitransforms.resampling.apply`` instead.
  """
- message = (
- "The `apply` method is deprecated. Please use `nitransforms.resampling.apply` instead."
- )
- warnings.warn(message, DeprecationWarning, stacklevel=2)
+ _msg = "This method is deprecated. Please use `nitransforms.resampling.apply` instead."
+ warnings.warn(_msg, DeprecationWarning, stacklevel=2)
  from .resampling import apply
 
  return apply(self, *args, **kwargs)