DEPR: deprecate .as_blocks()

closes #17302

doc/source/whatsnew/v0.21.0.txt

@@ -488,10 +488,9 @@ Other API Changes
 Deprecations
 ~~~~~~~~~~~~
 - :func:`read_excel()` has deprecated ``sheetname`` in favor of ``sheet_name`` for consistency with ``.to_excel()`` (:issue:`10559`).
-
 - ``pd.options.html.border`` has been deprecated in favor of ``pd.options.display.html.border`` (:issue:`15793`).
-
 - :func:`SeriesGroupBy.nth` has deprecated ``True`` in favor of ``'all'`` for its kwarg ``dropna`` (:issue:`11038`).
+- :func:`DataFrame.as_blocks` is deprecated as this is exposing the internal implementation (:issue:`17302`)
 
 .. _whatsnew_0210.prior_deprecations:
 

pandas/core/generic.py

@@ -3692,6 +3692,8 @@ def as_blocks(self, copy=True):
         Convert the frame to a dict of dtype -> Constructor Types that each has
         a homogeneous dtype.
 
+        .. deprecated:: 0.21.0
+
         NOTE: the dtypes of the blocks WILL BE PRESERVED HERE (unlike in
               as_matrix)
 
@@ -3705,6 +3707,10 @@ def as_blocks(self, copy=True):
         -------
         values : a dict of dtype -> Constructor Types
         """
+        warnings.warn("as_blocks is deprecated and will "
+                      "be removed in a future version",
+                      FutureWarning, stacklevel=2)
+
         self._consolidate_inplace()
 
         bd = {}
@@ -3722,7 +3728,11 @@ def as_blocks(self, copy=True):
 
     @property
     def blocks(self):
-        """Internal property, property synonym for as_blocks()"""
+        """
+        Internal property, property synonym for as_blocks()
+
+        .. deprecated:: 0.21.0
+        """
         return self.as_blocks()
 
     @deprecate_kwarg(old_arg_name='raise_on_error', new_arg_name='errors',
@@ -3931,13 +3941,12 @@ def convert_objects(self, convert_dates=True, convert_numeric=False,
         -------
         converted : same as input object
         """
-        from warnings import warn
         msg = ("convert_objects is deprecated.  To re-infer data dtypes for "
                "object columns, use {klass}.infer_objects()\nFor all "
                "other conversions use the data-type specific converters "
                "pd.to_datetime, pd.to_timedelta and pd.to_numeric."
                ).format(klass=self.__class__.__name__)
-        warn(msg, FutureWarning, stacklevel=2)
+        warnings.warn(msg, FutureWarning, stacklevel=2)
 
         return self._constructor(
             self._data.convert(convert_dates=convert_dates,
@@ -4310,9 +4319,9 @@ def replace(self, to_replace=None, value=None, inplace=False, limit=None,
             raise AssertionError("'to_replace' must be 'None' if 'regex' is "
                                  "not a bool")
         if axis is not None:
-            from warnings import warn
-            warn('the "axis" argument is deprecated and will be removed in'
-                 'v0.13; this argument has no effect')
+            warnings.warn('the "axis" argument is deprecated '
+                          'and will be removed in'
+                          'v0.13; this argument has no effect')
 
         self._consolidate_inplace()
 

pandas/tests/frame/test_block_internals.py

@@ -320,7 +320,11 @@ def test_copy_blocks(self):
         column = df.columns[0]
 
         # use the default copy=True, change a column
-        blocks = df.as_blocks()
+
+        # deprecated 0.21.0
+        with tm.assert_produces_warning(FutureWarning,
+                                        check_stacklevel=False):
+            blocks = df.as_blocks()
         for dtype, _df in blocks.items():
             if column in _df:
                 _df.loc[:, column] = _df[column] + 1
@@ -334,7 +338,11 @@ def test_no_copy_blocks(self):
         column = df.columns[0]
 
         # use the copy=False, change a column
-        blocks = df.as_blocks(copy=False)
+
+        # deprecated 0.21.0
+        with tm.assert_produces_warning(FutureWarning,
+                                        check_stacklevel=False):
+            blocks = df.as_blocks(copy=False)
         for dtype, _df in blocks.items():
             if column in _df:
                 _df.loc[:, column] = _df[column] + 1

pandas/tests/sparse/test_frame.py

@@ -1099,7 +1099,10 @@ def test_as_blocks(self):
         df = SparseDataFrame({'A': [1.1, 3.3], 'B': [nan, -3.9]},
                              dtype='float64')
 
-        df_blocks = df.blocks
+        # deprecated 0.21.0
+        with tm.assert_produces_warning(FutureWarning,
+                                        check_stacklevel=False):
+            df_blocks = df.blocks
         assert list(df_blocks.keys()) == ['float64']
         tm.assert_frame_equal(df_blocks['float64'], df)