feat: add AtIndexer getitems

bigframes/core/indexers.py

@@ -108,6 +108,16 @@ def __getitem__(self, key: int) -> bigframes.core.scalar.Scalar:
         return self._series.iloc[key]
 
 
+class AtSeriesIndexer:
+    def __init__(self, series: bigframes.series.Series):
+        self._series = series
+
+    def __getitem__(
+        self, key: LocSingleKey
+    ) -> Union[bigframes.core.scalar.Scalar, bigframes.series.Series]:
+        return self._series.loc[key]
+
+
 class LocDataFrameIndexer:
     def __init__(self, dataframe: bigframes.dataframe.DataFrame):
         self._dataframe = dataframe
@@ -221,6 +231,20 @@ def __getitem__(self, key: tuple) -> bigframes.core.scalar.Scalar:
         return column.iloc[key[0]]
 
 
+class AtDataFrameIndexer:
+    def __init__(self, dataframe: bigframes.dataframe.DataFrame):
+        self._dataframe = dataframe
+
+    def __getitem__(
+        self, key: tuple
+    ) -> Union[bigframes.core.scalar.Scalar, bigframes.series.Series]:
+        if not isinstance(key, tuple):
+            raise TypeError(
+                "DataFrame.at should be indexed by a (row label, column name) tuple."
+            )
+        return self._dataframe.loc[key]
+
+
 @typing.overload
 def _loc_getitem_series_or_dataframe(
     series_or_dataframe: bigframes.series.Series, key

bigframes/dataframe.py

@@ -259,6 +259,10 @@ def iloc(self) -> indexers.ILocDataFrameIndexer:
     def iat(self) -> indexers.IatDataFrameIndexer:
         return indexers.IatDataFrameIndexer(self)
 
+    @property
+    def at(self) -> indexers.AtDataFrameIndexer:
+        return indexers.AtDataFrameIndexer(self)
+
     @property
     def dtypes(self) -> pandas.Series:
         return pandas.Series(data=self._block.dtypes, index=self._block.column_labels)

bigframes/series.py

@@ -91,6 +91,10 @@ def iloc(self) -> bigframes.core.indexers.IlocSeriesIndexer:
     def iat(self) -> bigframes.core.indexers.IatSeriesIndexer:
         return bigframes.core.indexers.IatSeriesIndexer(self)
 
+    @property
+    def at(self) -> bigframes.core.indexers.AtSeriesIndexer:
+        return bigframes.core.indexers.AtSeriesIndexer(self)
+
     @property
     def name(self) -> blocks.Label:
         return self._name

tests/system/small/test_dataframe.py

@@ -2196,6 +2196,29 @@ def test_loc_single_index_no_duplicate(scalars_df_index, scalars_pandas_df_index
     )
 
 
+def test_at_with_duplicate(scalars_df_index, scalars_pandas_df_index):
+    scalars_df_index = scalars_df_index.set_index("string_col", drop=False)
+    scalars_pandas_df_index = scalars_pandas_df_index.set_index(
+        "string_col", drop=False
+    )
+    index = "Hello, World!"
+    bf_result = scalars_df_index.at[index, "int64_too"]
+    pd_result = scalars_pandas_df_index.at[index, "int64_too"]
+    pd.testing.assert_series_equal(
+        bf_result.to_pandas(),
+        pd_result,
+    )
+
+
+def test_at_no_duplicate(scalars_df_index, scalars_pandas_df_index):
+    scalars_df_index = scalars_df_index.set_index("int64_too", drop=False)
+    scalars_pandas_df_index = scalars_pandas_df_index.set_index("int64_too", drop=False)
+    index = -2345
+    bf_result = scalars_df_index.at[index, "string_col"]
+    pd_result = scalars_pandas_df_index.at[index, "string_col"]
+    assert bf_result == pd_result
+
+
 def test_loc_setitem_bool_series_scalar_new_col(scalars_dfs):
     scalars_df, scalars_pandas_df = scalars_dfs
     bf_df = scalars_df.copy()

tests/system/small/test_series.py

@@ -1953,6 +1953,16 @@ def test_series_iloc(scalars_df_index, scalars_pandas_df_index, start, stop, ste
     )
 
 
+def test_at(scalars_df_index, scalars_pandas_df_index):
+    scalars_df_index = scalars_df_index.set_index("int64_too", drop=False)
+    scalars_pandas_df_index = scalars_pandas_df_index.set_index("int64_too", drop=False)
+    index = -2345
+    bf_result = scalars_df_index["string_col"].at[index]
+    pd_result = scalars_pandas_df_index["string_col"].at[index]
+
+    assert bf_result == pd_result
+
+
 def test_iat(scalars_df_index, scalars_pandas_df_index):
     bf_result = scalars_df_index["int64_too"].iat[3]
     pd_result = scalars_pandas_df_index["int64_too"].iat[3]

third_party/bigframes_vendored/pandas/core/frame.py

@@ -2112,3 +2112,8 @@ def iloc(self):
     def iat(self):
         """Access a single value for a row/column pair by integer position."""
         raise NotImplementedError(constants.ABSTRACT_METHOD_ERROR_MESSAGE)
+
+    @property
+    def at(self):
+        """Access a single value for a row/column label pair."""
+        raise NotImplementedError(constants.ABSTRACT_METHOD_ERROR_MESSAGE)

third_party/bigframes_vendored/pandas/core/series.py

@@ -1833,3 +1833,8 @@ def iloc(self):
     def iat(self):
         """Access a single value for a row/column pair by integer position."""
         raise NotImplementedError(constants.ABSTRACT_METHOD_ERROR_MESSAGE)
+
+    @property
+    def at(self):
+        """Access a single value for a row/column label pair."""
+        raise NotImplementedError(constants.ABSTRACT_METHOD_ERROR_MESSAGE)