Addition of test to ensure observed pivots on categorial data are ind…

…eed faster than those which are set to False.

pandas/tests/reshape/test_pivot.py

@@ -2,6 +2,7 @@
 
 from collections import OrderedDict
 from datetime import date, datetime, timedelta
+import time
 
 import numpy as np
 import pytest
@@ -65,7 +66,7 @@ def test_pivot_table(self, observed):
  index + [columns])['D'].agg(np.mean).unstack()
  tm.assert_frame_equal(table, expected)
 
- def test_pivot_table_categorical_observed(self, observed):
+ def test_pivot_table_categorical_observed_equal(self, observed):
  # issue #24923
  df = pd.DataFrame({'col1': list('abcde'),
  'col2': list('fghij'),
@@ -84,6 +85,29 @@ def test_pivot_table_categorical_observed(self, observed):
 
  tm.assert_frame_equal(result, expected)
 
+ def test_pivot_table_categorical_observed_speed(self):
+ # issue #24923
+ df = pd.DataFrame({'col1': list('abcde'),
+ 'col2': list('fghij'),
+ 'col3': [1, 2, 3, 4, 5]})
+
+ df.col1 = df.col1.astype('category')
+ df.col2 = df.col1.astype('category')
+
+ start_time_observed_false = time.time()
+ df.pivot_table(index='col1', values='col3',
+ columns='col2', aggfunc=np.sum,
+ fill_value=0, observed=False)
+ total_time_observed_false = time.time() - start_time_observed_false
+
+ start_time_observed_true = time.time()
+ df.pivot_table(index='col1', values='col3',
+ columns='col2', aggfunc=np.sum,
+ fill_value=0, observed=True)
+ total_time_observed_true = time.time() - start_time_observed_true
+
+ assert total_time_observed_true < total_time_observed_false
+
  def test_pivot_table_nocols(self):
  df = DataFrame({'rows': ['a', 'b', 'c'],
  'cols': ['x', 'y', 'z'],