ENH: Improve short_reprs of classifier/normalizer.

GroupedRowTransform now shows the name of its transform, and Quantiles
shows the number of quantiles.

These are used by Pipeline.show_graph().

tests/pipeline/test_factor.py

@@ -4,6 +4,7 @@ Tests for Factor terms.
 from functools import partial
 from itertools import product
 from nose_parameterized import parameterized
+from unittest import TestCase
 
 from toolz import compose
 from numpy import (
@@ -822,3 +823,17 @@ class FactorTestCase(BasePipelineTestCase):
         self.assertIs(f.deciles(), f.quantiles(bins=10))
         self.assertIs(f.deciles(mask=m), f.quantiles(bins=10, mask=m))
         self.assertIsNot(f.deciles(), f.deciles(mask=m))
+
+
+class ShortReprTestCase(TestCase):
+    """
+    Tests for short_repr methods of Factors.
+    """
+
+    def test_demean(self):
+        r = F().demean().short_repr()
+        self.assertEqual(r, "GroupedRowTransform('demean')")
+
+    def test_zscore(self):
+        r = F().zscore().short_repr()
+        self.assertEqual(r, "GroupedRowTransform('zscore')")

zipline/pipeline/classifiers/classifier.py

@@ -78,6 +78,9 @@ class Quantiles(SingleInputMixin, Classifier):
         result[isnan(result)] = self.missing_value
         return result.astype(int64_dtype)
 
+    def short_repr(self):
+        return type(self).__name__ + '(%d)' % self.params['bins']
+
 
 class CustomClassifier(PositiveWindowLengthMixin, CustomTermMixin, Classifier):
     """

zipline/pipeline/factors/factor.py

@@ -576,8 +576,13 @@ class Factor(RestrictedDTypeMixin, ComputableTerm):
         --------
         :meth:`pandas.DataFrame.groupby`
         """
+        # This is a named function so that it has a __name__ for use in the
+        # graph repr of GroupedRowTransform.
+        def demean(row):
+            return row - nanmean(row)
+
         return GroupedRowTransform(
-            transform=lambda row: row - nanmean(row),
+            transform=demean,
             factor=self,
             mask=mask,
             groupby=groupby,
@@ -637,8 +642,13 @@ class Factor(RestrictedDTypeMixin, ComputableTerm):
         --------
         :meth:`pandas.DataFrame.groupby`
         """
+        # This is a named function so that it has a __name__ for use in the
+        # graph repr of GroupedRowTransform.
+        def zscore(row):
+            return (row - nanmean(row)) / nanstd(row)
+
         return GroupedRowTransform(
-            transform=lambda row: (row - nanmean(row)) / nanstd(row),
+            transform=zscore,
             factor=self,
             mask=mask,
             groupby=groupby,
@@ -1022,6 +1032,13 @@ class GroupedRowTransform(Factor):
             self.missing_value,
         )
 
+    @property
+    def transform_name(self):
+        return self._transform.__name__
+
+    def short_repr(self):
+        return type(self).__name__ + '(%r)' % self.transform_name
+
 
 class Rank(SingleInputMixin, Factor):
     """