RF - promote _dtype to public class variable

We use cls._dtype in various places; it should be part of the public
API.

Author: matthew-brett

nibabel/analyze.py

@@ -174,7 +174,7 @@ class AnalyzeHeader(WrapStruct):
     scaling
     '''
     # Copies of module-level definitions
-    _dtype = header_dtype
+    template_dtype = header_dtype
     _data_type_codes = data_type_codes
     # fields with recoders for their values
     _field_recoders = {'datatype': data_type_codes}

nibabel/nifti1.py

@@ -517,7 +517,7 @@ class Nifti1Header(SpmAnalyzeHeader):
     This class handles the header-preceding-data case.
     '''
     # Copies of module level definitions
-    _dtype = header_dtype
+    template_dtype = header_dtype
     _data_type_codes = data_type_codes
 
     # fields with recoders for their values
@@ -563,7 +563,7 @@ def copy(self):
 
     @classmethod
     def from_fileobj(klass, fileobj, endianness=None, check=True):
-        raw_str = fileobj.read(klass._dtype.itemsize)
+        raw_str = fileobj.read(klass.template_dtype.itemsize)
         hdr = klass(raw_str, endianness, check)
         # Read next 4 bytes to see if we have extensions.  The nifti standard
         # has this as a 4 byte string; if the first value is not zero, then we

nibabel/spm2analyze.py

@@ -30,7 +30,7 @@ class Spm2AnalyzeHeader(spm99.Spm99AnalyzeHeader):
     offset for data'''
 
     # Copies of module level definitions
-    _dtype = header_dtype
+    template_dtype = header_dtype
 
     def get_slope_inter(self):
         ''' Get data scaling (slope) and offset (intercept) from header data

nibabel/spm99analyze.py

@@ -37,7 +37,7 @@
 class SpmAnalyzeHeader(analyze.AnalyzeHeader):
     ''' Basic scaling Spm Analyze header '''
     # Copies of module level definitions
-    _dtype = header_dtype
+    template_dtype = header_dtype
 
     # data scaling capabilities
     has_data_slope = True

nibabel/tests/test_analyze.py

@@ -68,7 +68,7 @@ def test_general_init(self):
         assert_equal(hdr.get_zooms(), (1.0,))
 
     def test_header_size(self):
-        assert_equal(self.header_class._dtype.itemsize, 348)
+        assert_equal(self.header_class.template_dtype.itemsize, 348)
 
     def test_empty(self):
         hdr = self.header_class()

nibabel/tests/test_wrapstruct.py

@@ -47,10 +47,7 @@
 class MyWrapStruct(WrapStruct):
     """ An example binary header class """
     _field_recoders = {}
-    dtype_def = [
-        ('an_integer', 'i2'),
-        ('a_str', 'S10')]
-    _dtype = np.dtype(dtype_def)
+    template_dtype = np.dtype([('an_integer', 'i2'), ('a_str', 'S10')])
 
     @classmethod
     def guessed_endian(klass, hdr):

nibabel/wrapstruct.py

@@ -57,6 +57,11 @@
     .as_byteswapped(endianness)
     .write_to(fileobj)
     .from_fileobj(fileobj)
+    .default_structarr() - return default structured array
+    .guessed_endian(structarr) - return guessed endian code from this structarr
+
+Class variables:
+    template_dtype - native endian version of dtype for contained structarr
 
 Consistency checks
 ------------------
@@ -113,8 +118,7 @@ class WrapStructError(Exception):
 class WrapStruct(object):
     _field_recoders = {}
     # placeholder datatype
-    dtype_def = [('integer', 'i2')]
-    _dtype = np.dtype(dtype_def)
+    template_dtype = np.dtype([('integer', 'i2')])
 
     def __init__(self,
                  binaryblock=None,
@@ -149,17 +153,17 @@ def __init__(self,
             self._structarr = self.__class__.default_structarr(endianness)
             return
         # check size
-        if len(binaryblock) != self._dtype.itemsize:
+        if len(binaryblock) != self.template_dtype.itemsize:
             raise WrapStructError('Binary block is wrong size')
         wstr = np.ndarray(shape=(),
-                         dtype=self._dtype,
+                         dtype=self.template_dtype,
                          buffer=binaryblock)
         if endianness is None:
             endianness = self.__class__.guessed_endian(wstr)
         else:
             endianness = endian_codes[endianness]
         if endianness != native_code:
-            dt = self._dtype.newbyteorder(endianness)
+            dt = self.template_dtype.newbyteorder(endianness)
             wstr = np.ndarray(shape=(),
                              dtype=dt,
                              buffer=binaryblock)
@@ -184,7 +188,7 @@ def from_fileobj(klass, fileobj, endianness=None, check=True):
         wstr : WrapStruct object
            WrapStruct object initialized from data in fileobj
         '''
-        raw_str = fileobj.read(klass._dtype.itemsize)
+        raw_str = fileobj.read(klass.template_dtype.itemsize)
         return klass(raw_str, endianness, check)
 
     @property
@@ -321,12 +325,12 @@ def __iter__(self):
 
     def keys(self):
         ''' Return keys from structured data'''
-        return list(self._dtype.names)
+        return list(self.template_dtype.names)
 
     def values(self):
         ''' Return values from structured data'''
         data = self._structarr
-        return [data[key] for key in self._dtype.names]
+        return [data[key] for key in self.template_dtype.names]
 
     def items(self):
         ''' Return items from structured data'''
@@ -373,7 +377,7 @@ def guessed_endian(self, mapping):
     def default_structarr(klass, endianness=None):
         ''' Return structured array for default structure, with given endianness
         '''
-        dt = klass._dtype
+        dt = klass.template_dtype
         if endianness is not None:
             endianness = endian_codes[endianness]
             dt = dt.newbyteorder(endianness)