diff --git a/visualdl/backend/logic/pybind.cc b/visualdl/backend/logic/pybind.cc
index 2256542d880e2cc9199a4b9d6c27497491e8fb95..0be6d5cb56e66e1012228ab8c30748b7e73862fa 100644
--- a/visualdl/backend/logic/pybind.cc
+++ b/visualdl/backend/logic/pybind.cc
@@ -64,6 +64,7 @@ PYBIND11_MODULE(core, m) {
       .def("get_records", &vs::components::ScalarHelper<T>::GetRecords)   \
       .def("get_captions", &vs::components::ScalarHelper<T>::GetCaptions) \
       .def("get_ids", &vs::components::ScalarHelper<T>::GetIds)           \
+      .def("get_record_size", &vs::components::ScalarHelper<T>::GetSize)  \
       .def("get_timestamps", &vs::components::ScalarHelper<T>::GetTimestamps);
   ADD_SCALAR_TYPED_INTERFACE(int32_t, ScalarInt32);
   ADD_SCALAR_TYPED_INTERFACE(int64_t, ScalarInt64);
diff --git a/visualdl/backend/logic/sdk.cc b/visualdl/backend/logic/sdk.cc
index a2c7d638f847efc9af33487a725204a5b2a00df7..c676c5505ab215ca6e601b8307af443520238f2f 100644
--- a/visualdl/backend/logic/sdk.cc
+++ b/visualdl/backend/logic/sdk.cc
@@ -69,6 +69,7 @@ namespace components {
 
 template <typename T>
 void ScalarHelper<T>::SetCaptions(const std::vector<std::string> &captions) {
+  CHECK_EQ(data_->captions_size(), 0UL) << "the captions can set only once";
   for (int i = 0; i < captions.size(); i++) {
     data_->add_captions(captions[i]);
   }
diff --git a/visualdl/backend/logic/sdk.h b/visualdl/backend/logic/sdk.h
index 54a504325a1905f3a58c4e9a96817c64775275ec..d463e3cd5903afdfcaf3d2ccf413d5b8a54cc49b 100644
--- a/visualdl/backend/logic/sdk.h
+++ b/visualdl/backend/logic/sdk.h
@@ -133,6 +133,8 @@ public:
 
   std::vector<std::string> GetCaptions() const;
 
+  size_t GetSize() const { return data_->records_size(); }
+
 private:
   storage::Tablet *data_;
 };
diff --git a/visualdl/backend/python/__init__.py b/visualdl/backend/python/__init__.py
new file mode 100644
index 0000000000000000000000000000000000000000..e69de29bb2d1d6434b8b29ae775ad8c2e48c5391
diff --git a/visualdl/backend/python/summary.py b/visualdl/backend/python/summary.py
new file mode 100644
index 0000000000000000000000000000000000000000..59877aca69df649599e55aa112a4a8cf9d26c107
--- /dev/null
+++ b/visualdl/backend/python/summary.py
@@ -0,0 +1,106 @@
+__all__ = [
+    'set_storage',
+    'scalar',
+]
+import core
+
+im = core.im()
+
+dtypes = ("float", "double", "int32", "int64")
+
+
+def set_storage(dir):
+    '''
+    :param dir: str
+        directory of summary to write log.
+    :return: None
+    '''
+    im.storage().set_dir(dir)
+
+
+class _Scalar(object):
+    '''
+    Python syntax wrapper for the core.ScalarHelper object.
+    '''
+
+    def __init__(self, core_object):
+        self._core_object = core_object
+
+    def add(self, id, vs):
+        '''
+        add a scalar record
+        :param id: int
+        id in the x-corrdinate
+        :param vs: list
+        values
+        :return: None
+        '''
+        self._core_object.add_record(id, vs)
+
+    def set_captions(self, cs):
+        '''
+        set the captions, one caption for one line.
+        :param cs: list of str
+        :return: None
+        '''
+        self._core_object.set_captions(cs)
+
+    @property
+    def captions(self):
+        return self._core_object.get_captions()
+
+    @property
+    def records(self):
+        '''
+        get all the records, format like
+        [
+        [0.1, 0.2], # first record
+        [0.2, 0.3], # second record
+        # ...
+        ]
+        :return: list of list
+        '''
+        return self._core_object.get_records()
+
+    @property
+    def ids(self):
+        '''
+        get all the ids for the records
+        :return: list of int
+        '''
+        return self._core_object.get_ids()
+
+    @property
+    def timestamps(self):
+        '''
+        get all the timestamps for the records
+        :return: list of int
+        '''
+        return self._core_object.get_timestamps()
+
+    @property
+    def size(self):
+        return self._core_object.get_record_size()
+
+
+def scalar(tag, dtype='float'):
+    '''
+    create a scalar component.
+
+    :param tag: str
+        name of this component.
+    :param dtype: string
+        the data type that will be used in underlying storage.
+    :return: object of core.Tablet
+    '''
+    assert dtype in dtypes, "invalid dtype(%s), should be one of %s" % (
+        dtype, str(dtypes))
+    tablet = im.add_tablet(tag, -1)
+    dtype2obj = {
+        'float': tablet.as_float_scalar,
+        'double': tablet.as_double_scalar,
+        'int32': tablet.as_int32_scalar,
+        'int64': tablet.as_int64_scalar,
+    }
+    obj = dtype2obj[dtype]()
+    return _Scalar(obj)
diff --git a/visualdl/backend/python/test_summary.py b/visualdl/backend/python/test_summary.py
new file mode 100644
index 0000000000000000000000000000000000000000..24fec43f5690da88c4d0d8fd2bad697794e4b032
--- /dev/null
+++ b/visualdl/backend/python/test_summary.py
@@ -0,0 +1,44 @@
+import summary
+import numpy as np
+import unittest
+
+summary.set_storage("tmp_dir")
+
+once_flag = False
+
+
+class ScalarTester(unittest.TestCase):
+    def setUp(self):
+        global once_flag
+        self.scalar = summary.scalar("scalar0")
+        if not once_flag:
+            self.py_captions = ["train cost", "test cost"]
+            self.scalar.set_captions(self.py_captions)
+
+        self.py_records = []
+        self.py_ids = []
+        for i in range(10):
+            record = [0.1 * i, 0.2 * i]
+            id = i * 10
+            self.py_records.append(record)
+            self.py_ids.append(id)
+            if not once_flag:
+                self.scalar.add(id, record)
+        once_flag = True
+
+    def test_records(self):
+        self.assertEqual(self.scalar.size, len(self.py_records))
+        for i, record in enumerate(self.scalar.records):
+            self.assertTrue(np.isclose(record, self.py_records[i]).all())
+
+    def test_ids(self):
+        self.assertEqual(len(self.py_ids), self.scalar.size)
+        for i, id in enumerate(self.scalar.ids):
+            self.assertEqual(self.py_ids[i], id)
+
+    def test_captions(self):
+        self.assertEqual(self.scalar.captions, self.py_captions)
+
+
+if __name__ == '__main__':
+    unittest.main()