Add Python bindings for get_json_object

python/cudf/cudf/_lib/cpp/strings/json.pxd

@@ -0,0 +1,16 @@
+# Copyright (c) 2021, NVIDIA CORPORATION.
+
+from cudf._lib.cpp.column.column_view cimport column_view
+from cudf._lib.cpp.scalar.scalar cimport string_scalar
+from libcpp.memory cimport unique_ptr
+from libcpp.string cimport string
+
+from cudf._lib.cpp.column.column cimport column
+from cudf._lib.cpp.scalar.scalar cimport scalar
+
+
+cdef extern from "cudf/strings/json.hpp" namespace "cudf::strings" nogil:
+    cdef unique_ptr[column] get_json_object(
+        column_view col,
+        string_scalar json_path,
+    ) except +

python/cudf/cudf/_lib/strings/json.pyx

@@ -0,0 +1,36 @@
+# Copyright (c) 2021, NVIDIA CORPORATION.
+
+from libcpp.memory cimport unique_ptr
+from libcpp.utility cimport move
+from cudf._lib.cpp.column.column_view cimport column_view
+from cudf._lib.cpp.scalar.scalar cimport string_scalar
+from cudf._lib.cpp.types cimport size_type
+from cudf._lib.column cimport Column
+from cudf._lib.scalar cimport DeviceScalar
+from cudf._lib.cpp.column.column cimport column
+
+from cudf._lib.cpp.strings.json cimport (
+    get_json_object as cpp_get_json_object
+)
+
+
+def get_json_object(Column col, object py_json_path):
+    """
+    Apply a JSONPath string to all rows in an input column
+    of json strings.
+    """
+    cdef unique_ptr[column] c_result
+
+    cdef column_view col_view = col.view()
+    cdef DeviceScalar json_path = py_json_path.device_value
+
+    cdef const string_scalar* scalar_json_path = <const string_scalar*>(
+        json_path.get_raw_ptr()
+    )
+    with nogil:
+        c_result = move(cpp_get_json_object(
+            col_view,
+            scalar_json_path[0],
+        ))
+
+    return Column.from_unique_ptr(move(c_result))

python/cudf/cudf/core/column/string.py

@@ -107,6 +107,7 @@
     startswith_multiple as cpp_startswith_multiple,
 )
 from cudf._lib.strings.findall import findall as cpp_findall
+from cudf._lib.strings.json import get_json_object as cpp_get_json_object
 from cudf._lib.strings.padding import (
     PadSide,
     center as cpp_center,
@@ -1998,6 +1999,29 @@ def get(self, i: int = 0) -> ParentType:
 
         return self._return_or_inplace(cpp_string_get(self._column, i))
 
+    def extract_json(self, json_path):
+        """
+        Applies a JSONPath string to an input strings column
+        where each row in the column is a valid json string
+
+        Parameters
+        ----------
+        json_path: str
+            The JSONPath string to be applied to each row
+            of the input column
+
+        Returns
+        -------
+        Column: New strings column containing the retrieved json object strings
+
+        Examples
+        --------
+
+        """
+        return self._return_or_inplace(
+            cpp_get_json_object(self._column, cudf.Scalar(json_path, "str"))
+        )
+
     def split(
         self, pat: str = None, n: int = -1, expand: bool = None
     ) -> ParentType:

python/cudf/cudf/tests/test_string.py

@@ -2931,3 +2931,27 @@ def test_string_slice_with_mask():
     assert_eq(actual._column.null_count, expected._column.null_count)
 
     assert_eq(actual, expected)
+
+
+@pytest.mark.parametrize(
+    "json_path", ["$.store", "$.store.book" "$.store.book[0].category"]
+)
+def test_string_get_json_object(json_path):
+    sr = cudf.Series(
+        [
+            """{"store": {
+    "book": [
+      { "category": "reference",
+        "author": "Nigel Rees",
+        "title": "Sayings of the Century",
+        "price": 8.95
+      },
+      { "category": "fiction",
+        "author": "Evelyn Waugh",
+        "title": "Sword of Honour",
+        "price": 12.99
+      },
+    ]}}"""
+        ]
+    )
+    sr.str.extract_json(json_path)