AlexanderKalistratov · Apr 23, 2020 · Mar 19, 2020 · Mar 20, 2020 · Mar 20, 2020 · Mar 26, 2020
diff --git a/examples/dataframe/dataframe_at.py b/examples/dataframe/dataframe_at.py
@@ -0,0 +1,39 @@
+# *****************************************************************************
+# Copyright (c) 2020, Intel Corporation All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+#     Redistributions of source code must retain the above copyright notice,
+#     this list of conditions and the following disclaimer.
+#
+#     Redistributions in binary form must reproduce the above copyright notice,
+#     this list of conditions and the following disclaimer in the documentation
+#     and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+# EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+# PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+# OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+# WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+# OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+# EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+# *****************************************************************************
+
+
+import pandas as pd
+from numba import njit
+
+
+@njit
+def dataframe_at():
+    df = pd.DataFrame({'A': [1.0, 2.0, 3.0, 1.0], 'B': [4, 5, 6, 7], 'C': ['a', 'b', 'c', 'd']})
+
+    return df.at[1, 'C']  # ['b']
+
+
+print(dataframe_at())
diff --git a/sdc/datatypes/hpat_pandas_dataframe_functions.py b/sdc/datatypes/hpat_pandas_dataframe_functions.py
@@ -38,7 +38,7 @@
 
 from pandas.core.indexing import IndexingError
 
-from numba import types
+from numba import types, prange
 from numba.special import literally
 from numba.typed import List, Dict
 from numba.errors import TypingError
@@ -1759,13 +1759,73 @@ def _df_getitem_unicode_idx_impl(self, idx):
     ty_checker.raise_exc(idx, expected_types, 'idx')
 
 
+def df_getitem_tuple_at_codegen(self, row, col):
+    """
+    Example of generated implementation:
+        def _df_getitem_tuple_at_impl(self, idx):
+            row, _ = idx
+            check_row = False
+            for i in prange(len(self._dataframe.index)):
+                if self._dataframe.index[i] == row:
+                    check_row = True
+            if check_row:
+                data = self._dataframe._data[2]
+                res_data = pandas.Series(data, index=self._dataframe.index)
+                return res_data.at[row]
+            raise IndexingError('Index is out of bounds for axis')
+    """
+    func_lines = ['def _df_getitem_tuple_at_impl(self, idx):']
+    for i in range(len(self.columns)):
+        if self.columns[i] == col:
+            func_lines += [
+                '  row, _ = idx',
+                '  check_row = False',
+                '  for i in prange(len(self._dataframe.index)):',
+                '    if self._dataframe.index[i] == row:',
+                '      check_row = True',
+                '  if check_row:',
+                f'    data = self._dataframe._data[{i}]',
+                '    res_data = pandas.Series(data, index=self._dataframe.index)',
+                '    return res_data.at[row]',
+                '  raise IndexingError("Index is out of bounds for axis")'
+            ]
+            break
+    else:
+        raise IndexingError('Index is out of bounds for axis')
+
+    func_text = '\n'.join(func_lines)
+
+    global_vars = {'pandas': pandas,
+                   'prange': prange,
+                   'IndexingError': IndexingError}
+
+    return func_text, global_vars
+
+
+def gen_df_getitem_tuple_at_impl(self, row, col):
+    func_text, global_vars = df_getitem_tuple_at_codegen(self, row, col)
+    loc_vars = {}
+    exec(func_text, global_vars, loc_vars)
+    _reduce_impl = loc_vars['_df_getitem_tuple_at_impl']
+
+    return _reduce_impl
+
+
 @sdc_overload(operator.getitem)
 def sdc_pandas_dataframe_accessor_getitem(self, idx):
     if not isinstance(self, DataFrameGetitemAccessorType):
         return None
 
     accessor = self.accessor.literal_value
 
+    if accessor == 'at':
+        if isinstance(idx, types.Tuple) and isinstance(idx[1], types.Literal):
+            row = idx[0]
+            col = idx[1].literal_value
+            return gen_df_getitem_tuple_at_impl(self.dataframe, row, col)
+
+        raise TypingError('Operator getitem(). The index must be a row and literal column. Given: {}'.format(idx))
+
     if accessor == 'iat':
         if isinstance(idx, types.Tuple) and isinstance(idx[1], types.Literal):
             col = idx[1].literal_value
@@ -1836,6 +1896,57 @@ def sdc_pandas_dataframe_iat_impl(self):
     return sdc_pandas_dataframe_iat_impl
 
 
+@sdc_overload_attribute(DataFrameType, 'at')
+def sdc_pandas_dataframe_at(self):
+    """
+    Intel Scalable Dataframe Compiler User Guide
+    ********************************************
+
+    Limitations
+    -----------
+    - Parameter ``column`` in ``idx`` must be a literal value.
+
+    Pandas API: pandas.DataFrame.at
+
+    Examples
+    --------
+    .. literalinclude:: ../../../examples/dataframe/dataframe_at.py
+       :language: python
+       :lines: 28-
+       :caption: Access a single value for a row/column label pair.
+       :name: ex_dataframe_at
+
+    .. command-output:: python ./dataframe/dataframe_at.py
+       :cwd: ../../../examples
+
+    .. seealso::
+
+        :ref:`DataFrame.iat <pandas.DataFrame.iat>`
+            Access a single value for a row/column pair by integer position.
+
+        :ref:`DataFrame.loc <pandas.DataFrame.loc>`
+            Access a group of rows and columns by label(s).
+
+        :ref:`Series.at <pandas.Series.at>`
+            Access a single value using a label.
+
+    Intel Scalable Dataframe Compiler Developer Guide
+    *************************************************
+    Pandas DataFrame method :meth:`pandas.DataFrame.at` implementation.
+
+    .. only:: developer
+        Test: python -m sdc.runtests -k sdc.tests.test_dataframe.TestDataFrame.test_df_at*
+    """
+
+    ty_checker = TypeChecker('Attribute at().')
+    ty_checker.check(self, DataFrameType)
+
+    def sdc_pandas_dataframe_at_impl(self):
+        return dataframe_getitem_accessor_init(self, 'at')
+
+    return sdc_pandas_dataframe_at_impl
+
+
 @sdc_overload_method(DataFrameType, 'pct_change')
 def pct_change_overload(df, periods=1, fill_method='pad', limit=None, freq=None):
     """

diff --git a/sdc/tests/test_dataframe.py b/sdc/tests/test_dataframe.py
@@ -1100,6 +1100,33 @@ def test_impl(df):
         msg = 'Index is out of bounds for axis'
         self.assertIn(msg, str(raises.exception))
 
+    def test_df_at(self):
+        def test_impl(df, n):
+            return df.at[n, 'C']
+
+        sdc_func = sdc.jit(test_impl)
+        idx = [3, 4, 1, 2, 0]
+        n_cases = [0, 2]
+        df = pd.DataFrame({"A": [3.2, 4.4, 7.0, 3.3, 1.0],
+                           "B": [3, 4, 1, 0, 222],
+                           "C": ['a', 'dd', 'c', '12', 'ddf']}, index=idx)
+        for n in n_cases:
+            self.assertEqual(sdc_func(df, n), test_impl(df, n))
+
+    def test_df_at_value_error(self):
+        def test_impl(df):
+            return df.at[1, 'D']
+        sdc_func = sdc.jit(test_impl)
+        idx = [3, 4, 1, 2, 0]
+        df = pd.DataFrame({"A": [3.2, 4.4, 7.0, 3.3, 1.0],
+                           "B": [3, 4, 1, 0, 222],
+                           "C": [3, 4, 2, 6, 1]}, index=idx)
+
+        with self.assertRaises(TypingError) as raises:
+            sdc_func(df)
+        msg = 'Index is out of bounds for axis'
+        self.assertIn(msg, str(raises.exception))
+
     def test_df_head(self):
         def get_func(n):
             def impl(a):