RF - move fieldname recoding to header class

The field_recoders is a bit specific to headers; move to the header
classes, leave wrapstruct with generic stub interface to get_value_label

Author: matthew-brett

nibabel/analyze.py

@@ -357,13 +357,20 @@ def get_value_label(self, fieldname):
         label : str
            label for code value in header field `fieldname`
 
+        Raises
+        ------
+        ValueError : if field is not coded
+
         Examples
         --------
         >>> hdr = AnalyzeHeader()
         >>> hdr.get_value_label('datatype')
         'float32'
         '''
-        return super(AnalyzeHeader, self).get_value_label(fieldname)
+        if not fieldname in self._field_recoders:
+            raise ValueError('%s not a coded field' % fieldname)
+        code = int(self._structarr[fieldname])
+        return self._field_recoders[fieldname].label[code]
 
     @classmethod
     def from_header(klass, header=None, check=True):

nibabel/tests/test_wrapstruct.py

@@ -45,8 +45,8 @@
 
 
 class MyWrapStruct(WrapStruct):
-    """ An example binary header class """
-    _field_recoders = {}
+    """ An example wrapped struct class """
+    _field_recoders = {} # for recoding values for str
     template_dtype = np.dtype([('an_integer', 'i2'), ('a_str', 'S10')])
 
     @classmethod
@@ -68,6 +68,12 @@ def _get_checks(klass):
         return (klass._chk_integer,
                 klass._chk_string)
 
+    def get_value_label(self, fieldname):
+        if not fieldname in self._field_recoders:
+            raise ValueError('%s not a coded field' % fieldname)
+        code = int(self._structarr[fieldname])
+        return self._field_recoders[fieldname].label[code]
+
     ''' Check functions in format expected by BatteryRunner class '''
     @staticmethod
     def _chk_integer(hdr, fix=False):

nibabel/wrapstruct.py

@@ -50,6 +50,7 @@
     .__str__
     .__eq__
     .__ne__
+    .get_value_label(name)
 
 Class methods::
 
@@ -116,7 +117,6 @@ class WrapStructError(Exception):
 
 
 class WrapStruct(object):
-    _field_recoders = {}
     # placeholder datatype
     template_dtype = np.dtype([('integer', 'i2')])
 
@@ -427,11 +427,12 @@ def get_value_label(self, fieldname):
         -------
         label : str
            label for code value in field `fieldname`
+
+        Raises
+        ------
+        ValueError : if fieldname not coded
         '''
-        if not fieldname in self._field_recoders:
-            raise ValueError('%s not a coded field' % fieldname)
-        code = int(self._structarr[fieldname])
-        return self._field_recoders[fieldname].label[code]
+        raise ValueError('%s not a coded field' % fieldname)
 
     def as_byteswapped(self, endianness=None):
         ''' return new byteswapped object with given ``endianness``