[TD-6241]<fix>: fix unexpected nan while inserting None as float/doub… (#7486)

* [TD-6241]<fix>: fix unexpected nan while inserting None as float/double type

* [TD-6241]<fix>: fix binary bind error in python connector

src/connector/python/taos/bind.py

@@ -300,29 +300,8 @@ class TaosMultiBind(ctypes.Structure):
         self.buffer = cast(buffer, c_void_p)
         self.num = len(values)
 
-    def binary(self, values):
+    def _str_to_buffer(self, values):
         self.num = len(values)
-        self.buffer = cast(c_char_p("".join(filter(_is_not_none, values)).encode("utf-8")), c_void_p)
-        self.length = (c_int * len(values))(*[len(value) if value is not None else 0 for value in values])
-        self.buffer_type = FieldType.C_BINARY
-        self.is_null = cast((c_byte * self.num)(*[1 if v == None else 0 for v in values]), c_char_p)
-
-    def timestamp(self, values, precision=PrecisionEnum.Milliseconds):
-        try:
-            buffer = cast(values, c_void_p)
-        except:
-            buffer_type = c_int64 * len(values)
-            buffer = buffer_type(*[_datetime_to_timestamp(value, precision) for value in values])
-
-        self.buffer_type = FieldType.C_TIMESTAMP
-        self.buffer = cast(buffer, c_void_p)
-        self.buffer_length = sizeof(c_int64)
-        self.num = len(values)
-
-    def nchar(self, values):
-        # type: (list[str]) -> None
-        self.num = len(values)
-        self.buffer_type = FieldType.C_NCHAR
         is_null = [1 if v == None else 0 for v in values]
         self.is_null = cast((c_byte * self.num)(*is_null), c_char_p)
         
@@ -356,6 +335,26 @@ class TaosMultiBind(ctypes.Structure):
             )
         self.length = (c_int32 * len(values))(*[len(b) if b is not None else 0 for b in _bytes])
         self.buffer_length = buffer_length
+    def binary(self, values):
+        self.buffer_type = FieldType.C_BINARY
+        self._str_to_buffer(values)
+
+    def timestamp(self, values, precision=PrecisionEnum.Milliseconds):
+        try:
+            buffer = cast(values, c_void_p)
+        except:
+            buffer_type = c_int64 * len(values)
+            buffer = buffer_type(*[_datetime_to_timestamp(value, precision) for value in values])
+
+        self.buffer_type = FieldType.C_TIMESTAMP
+        self.buffer = cast(buffer, c_void_p)
+        self.buffer_length = sizeof(c_int64)
+        self.num = len(values)
+
+    def nchar(self, values):
+        # type: (list[str]) -> None
+        self.buffer_type = FieldType.C_NCHAR
+        self._str_to_buffer(values)
 
     def tinyint_unsigned(self, values):
         self.buffer_type = FieldType.C_TINYINT_UNSIGNED

src/connector/python/taos/constants.py

@@ -3,6 +3,9 @@
 """Constants in TDengine python
 """
 
+import ctypes, struct
+
+
 class FieldType(object):
     """TDengine Field Types"""
 
@@ -33,8 +36,8 @@ class FieldType(object):
     C_INT_UNSIGNED_NULL = 4294967295
     C_BIGINT_NULL = -9223372036854775808
     C_BIGINT_UNSIGNED_NULL = 18446744073709551615
-    C_FLOAT_NULL = float("nan")
-    C_DOUBLE_NULL = float("nan")
+    C_FLOAT_NULL = ctypes.c_float(struct.unpack("<f", b"\x00\x00\xf0\x7f")[0])
+    C_DOUBLE_NULL = ctypes.c_double(struct.unpack("<d", b"\x00\x00\x00\x00\x00\xff\xff\x7f")[0])
     C_BINARY_NULL = bytearray([int("0xff", 16)])
     # Timestamp precision definition
     C_TIMESTAMP_MILLI = 0