Address comments.

1. Ensure we return named tuples in more cases (when using python >=
   3.7)
2. Move test around to be with the itertuples test
3. Update docstring with the new behaviour.

Author: simongibbons

pandas/core/frame.py

@@ -38,6 +38,7 @@
 
 from pandas._libs import algos as libalgos, lib
 from pandas._typing import Axes, Dtype, FilePathOrBuffer
+from pandas.compat import PY37
 from pandas.compat._optional import import_optional_dependency
 from pandas.compat.numpy import function as nv
 from pandas.util._decorators import (
@@ -975,7 +976,8 @@ def itertuples(self, index=True, name="Pandas"):
         -----
         The column names will be renamed to positional names if they are
         invalid Python identifiers, repeated, or start with an underscore.
-        With a large number of columns (>255), regular tuples are returned.
+        On python versions < 3.7 regular tuples are returned for DataFrames
+        with a large number of columns (>254).
 
         Examples
         --------
@@ -1018,8 +1020,9 @@ def itertuples(self, index=True, name="Pandas"):
         # use integer indexing because of possible duplicate column names
         arrays.extend(self.iloc[:, k] for k in range(len(self.columns)))
 
-        # Python versions before 3.7 support at most 255 arguments to constructor
-        if name is not None and len(self.columns) + index < 255:
+        # Python versions before 3.7 support at most 255 arguments to constructors
+        can_return_named_tuples = PY37 or len(self.columns) + index < 255
+        if name is not None and can_return_named_tuples:
             itertuple = collections.namedtuple(name, fields, rename=True)
             return map(itertuple._make, zip(*arrays))
 

pandas/tests/frame/test_api.py

@@ -7,6 +7,7 @@
 
 import pandas as pd
 from pandas import Categorical, DataFrame, Series, compat, date_range, timedelta_range
+from pandas.compat import PY37
 import pandas.util.testing as tm
 
 
@@ -264,6 +265,25 @@ def test_itertuples(self, float_frame):
         assert not hasattr(tup3, "_fields")
         assert isinstance(tup3, tuple)
 
+    def test_itertuples_fallback_to_regular_tuples(self):
+        # GH 28282
+
+        df_254_columns = DataFrame([{f"foo_{i}": f"bar_{i}" for i in range(254)}])
+        result_254_columns = next(df_254_columns.itertuples(index=False))
+        assert isinstance(result_254_columns, tuple)
+        assert result_254_columns.foo_1 == "bar_1"
+
+        df_255_columns = DataFrame([{f"foo_{i}": f"bar_{i}" for i in range(255)}])
+        result_255_columns = next(df_255_columns.itertuples(index=False))
+        assert isinstance(result_255_columns, tuple)
+
+        # Dataframes with >=255 columns will fallback to regular tuples on python < 3.7
+        if not PY37:
+            with pytest.raises(AttributeError):
+                result_255_columns.foo_1
+        else:
+            assert result_254_columns.foo_1 == "bar_1"
+
     def test_sequence_like_with_categorical(self):
 
         # GH 7839
@@ -288,22 +308,6 @@ def test_sequence_like_with_categorical(self):
         for c, col in df.items():
             str(s)
 
-    def test_itertuples_fallback_to_regular_tuples(self):
-        # GH 28282
-
-        df_254_columns = DataFrame([{f"foo_{i}": f"bar_{i}" for i in range(254)}])
-        result_254_columns = next(df_254_columns.itertuples(index=False))
-        assert isinstance(result_254_columns, tuple)
-        assert result_254_columns.foo_1 == "bar_1"
-
-        df_255_columns = DataFrame([{f"foo_{i}": f"bar_{i}" for i in range(255)}])
-        result_255_columns = next(df_255_columns.itertuples(index=False))
-        assert isinstance(result_255_columns, tuple)
-
-        # Dataframes with >=255 columns will fallback to regular tuples
-        with pytest.raises(AttributeError):
-            result_255_columns.foo_1
-
     def test_len(self, float_frame):
         assert len(float_frame) == len(float_frame.index)