Add new interface schema & len for filereader

docs/api/api_python/mindrecord/mindspore.mindrecord.FileReader.rst

@@ -29,3 +29,17 @@
 
         异常：
             - **MRMUnsupportedSchemaError** - 当schema无效。
+
+    .. py:method:: schema()
+
+        返回当前MindRecord文件的Schema信息。
+
+        返回：
+            dict，Schema信息。
+
+    .. py:method:: len()
+
+        返回当前MindRecord文件的样本个数。
+
+        返回：
+            int，样本个数。

mindspore/ccsrc/minddata/mindrecord/common/shard_pybind.cc

@@ -181,7 +181,8 @@ void BindShardReader(const py::module *m) {
                           });
            return res;
          })
-    .def("close", &ShardReader::Close);
+    .def("close", &ShardReader::Close)
+    .def("len", &ShardReader::GetNumRows);
 }
 
 void BindShardIndexGenerator(const py::module *m) {

mindspore/python/mindspore/mindrecord/filereader.py

@@ -100,3 +100,21 @@ class FileReader:
     def close(self):
         """Stop reader worker and close file."""
         self._reader.close()
+
+    def schema(self):
+        """
+        Get the schema of the MindRecord.
+
+        Returns:
+            dict, the schema info.
+        """
+        return self._header.schema
+
+    def len(self):
+        """
+        Get the number of the samples in MindRecord.
+
+        Returns:
+            int, the number of the samples in MindRecord.
+        """
+        return self._reader.len()

mindspore/python/mindspore/mindrecord/shardreader.py

@@ -106,3 +106,12 @@ class ShardReader:
     def close(self):
         """close MindRecord File."""
         self._reader.close()
+
+    def len(self):
+        """
+        Get the number of the samples in MindRecord.
+
+        Returns:
+            int, the number of the samples in MindRecord.
+        """
+        return self._reader.len()

tests/ut/python/mindrecord/test_mindrecord_base.py

@@ -1270,3 +1270,83 @@ def test_cv_file_overwrite_exception_02():
         writer.write_raw_data(data)
     assert 'Invalid file, mindrecord files already exist. Please check file path:' in str(err.value)
     remove_multi_files(mindrecord_file_name, FILES_NUM)
+
+
+def test_file_writer_schema_len(file_name=None, remove_file=True):
+    """
+    Feature: FileWriter
+    Description: writer for schema and len
+    Expectation: SUCCESS
+    """
+    if not file_name:
+        file_name = os.environ.get('PYTEST_CURRENT_TEST').split(':')[-1].split(' ')[0]
+
+    ## single mindrecord file
+    # 1. empty file
+    remove_one_file(file_name)
+    remove_one_file(file_name + ".db")
+    writer = FileWriter(file_name, 1)
+    cv_schema_json = {"file_name": {"type": "string"},
+                      "label": {"type": "int64"}, "data": {"type": "bytes"}}
+    writer.add_schema(cv_schema_json, "img_schema")
+    writer.commit()
+
+    # get the schema & len
+    reader = FileReader(file_name)
+    assert cv_schema_json == reader.schema()
+    assert reader.len() == 0
+    if remove_file:
+        remove_one_file(file_name)
+        remove_one_file(file_name + ".db")
+
+    # 2. with 10 samples
+    remove_one_file(file_name)
+    remove_one_file(file_name + ".db")
+    writer = FileWriter(file_name, 1)
+    cv_schema_json = {"file_name": {"type": "string"},
+                      "label": {"type": "int64"}, "data": {"type": "bytes"}}
+    data = get_data("../data/mindrecord/testImageNetData/")
+    writer.add_schema(cv_schema_json, "img_schema")
+    writer.write_raw_data(data)
+    writer.commit()
+
+    # get the schema & len
+    reader = FileReader(file_name)
+    assert cv_schema_json == reader.schema()
+    assert reader.len() == 10
+    if remove_file:
+        remove_one_file(file_name)
+        remove_one_file(file_name + ".db")
+
+    ## multi mindrecord file
+    # 1. empty file
+    remove_multi_files(file_name, FILES_NUM)
+    writer = FileWriter(file_name, FILES_NUM)
+    cv_schema_json = {"file_name": {"type": "string"},
+                      "label": {"type": "int64"}, "data": {"type": "bytes"}}
+    writer.add_schema(cv_schema_json, "img_schema")
+    writer.commit()
+
+    # get the schema & len
+    reader = FileReader(file_name + "0")
+    assert cv_schema_json == reader.schema()
+    assert reader.len() == 0
+    if remove_file:
+        remove_multi_files(file_name, FILES_NUM)
+
+    # 2. with samples
+    remove_multi_files(file_name, FILES_NUM)
+    writer = FileWriter(file_name, FILES_NUM)
+    cv_schema_json = {"file_name": {"type": "string"},
+                      "label": {"type": "int64"}, "data": {"type": "bytes"}}
+    data = get_data("../data/mindrecord/testImageNetData/")
+    writer.add_schema(cv_schema_json, "img_schema")
+    writer.write_raw_data(data)
+    writer.commit()
+
+    # get the schema & len
+    reader = FileReader(file_name + "0")
+    assert cv_schema_json == reader.schema()
+    assert reader.len() == 10
+    if remove_file:
+        remove_multi_files(file_name, FILES_NUM)