Add samply.py for example testing, modify get_values_for_csv to fix extra decimal points

Author: akj2018

pandas/core/indexes/base.py

@@ -7758,10 +7758,11 @@ def get_values_for_csv(
             if not quoting:
                 values = values.astype(str)
             else:
-                values = np.array(values, dtype="object")
+                values = np.array(values, dtype="str")   # Convert float16 -> string
+                values = values.astype(float, copy=False)   # Parse string -> Python float64
 
-            values[mask] = na_rep
             values = values.astype(object, copy=False)
+            values[mask] = na_rep
             return values
 
         from pandas.io.formats.format import FloatArrayFormatter

sample.py

@@ -0,0 +1,29 @@
+import pandas as pd
+import numpy as np
+import csv
+
+df = pd.DataFrame({"col": [8.5557]}, dtype=np.float32)
+
+print(df.to_csv())
+
+print(df.to_csv(quoting=csv.QUOTE_NONNUMERIC))
+
+values = np.array([8.57], dtype="float32")
+print(values)
+# [8.57]
+
+print(np.array(values, dtype="object"))
+# [8.569999694824219]
+
+print(np.array(values, dtype="str"))
+
+
+# Original array in float32
+float32_arr = np.array([1.2345678, 2.3456789], dtype=np.float32)
+
+# Convert to object
+object_arr = float32_arr.astype(object)
+
+print("Original float32 array:", float32_arr)
+print("Object array:", object_arr)
+print("Data type of object_arr:", object_arr.dtype)