Simplify the code for extension dtypes by not attempting to convert them

Author: AnnaDaglis

pandas/core/dtypes/cast.py

@@ -1051,46 +1051,43 @@ def convert_dtypes(
     dtype
         new dtype
     """
+    inferred_dtype = input_array.dtype
+
     if convert_string or convert_integer or convert_boolean:
-        try:
-            inferred_dtype = lib.infer_dtype(input_array)
-        except ValueError:
-            # Required to catch due to Period.  Can remove once GH 23553 is fixed
-            inferred_dtype = input_array.dtype
+        if not is_extension_array_dtype(input_array.dtype):
+            try:
+                inferred_dtype = lib.infer_dtype(input_array)
+            except ValueError:
+                # Required to catch due to Period.  Can remove once GH 23553 is fixed
+                inferred_dtype = input_array.dtype
 
-        if not convert_string and is_string_dtype(inferred_dtype):
-            inferred_dtype = input_array.dtype
+            if not convert_string and is_string_dtype(inferred_dtype):
+                inferred_dtype = input_array.dtype
 
-        if convert_integer:
-            target_int_dtype = "Int64"
+            if convert_integer:
+                target_int_dtype = "Int64"
 
-            if is_integer_dtype(input_array.dtype) and not is_extension_array_dtype(
-                input_array.dtype
-            ):
-                from pandas.core.arrays.integer import _dtypes
+                if is_integer_dtype(input_array.dtype):
+                    from pandas.core.arrays.integer import _dtypes
 
-                inferred_dtype = _dtypes.get(input_array.dtype.name, target_int_dtype)
-            if not is_integer_dtype(input_array.dtype) and is_numeric_dtype(
-                input_array.dtype
-            ):
-                inferred_dtype = target_int_dtype
+                    inferred_dtype = _dtypes.get(
+                        input_array.dtype.name, target_int_dtype
+                    )
+                if not is_integer_dtype(input_array.dtype) and is_numeric_dtype(
+                    input_array.dtype
+                ):
+                    inferred_dtype = target_int_dtype
 
-        else:
-            if is_integer_dtype(inferred_dtype):
-                inferred_dtype = input_array.dtype
-
-        if convert_boolean:
-            if is_bool_dtype(input_array.dtype) and (
-                (not is_extension_array_dtype(input_array.dtype))
-                or (input_array.dtype == pd.BooleanDtype())
-            ):
-                inferred_dtype = "boolean"
-        else:
-            if isinstance(inferred_dtype, str) and inferred_dtype == "boolean":
-                inferred_dtype = input_array.dtype
+            else:
+                if is_integer_dtype(inferred_dtype):
+                    inferred_dtype = input_array.dtype
 
-    else:
-        inferred_dtype = input_array.dtype
+            if convert_boolean:
+                if is_bool_dtype(input_array.dtype):
+                    inferred_dtype = "boolean"
+            else:
+                if isinstance(inferred_dtype, str) and inferred_dtype == "boolean":
+                    inferred_dtype = input_array.dtype
 
     return inferred_dtype
 

pandas/core/series.py

@@ -4344,11 +4344,9 @@ def _convert_dtypes(
         convert_integer: bool = True,
         convert_boolean: bool = True,
     ) -> "Series":
-        input_series = self
+        input_series = self.copy()
         if infer_objects:
             input_series = input_series.infer_objects()
-            if is_object_dtype(input_series):
-                input_series = input_series.copy()
 
         if convert_string or convert_integer or convert_boolean:
             inferred_dtype = convert_dtypes(
@@ -4357,9 +4355,9 @@ def _convert_dtypes(
             try:
                 result = input_series.astype(inferred_dtype)
             except TypeError:
-                result = input_series.copy()
+                result = input_series
         else:
-            result = input_series.copy()
+            result = input_series
         return result
 
     @Appender(generic._shared_docs["isna"] % _shared_doc_kwargs)

pandas/tests/series/methods/test_convert_dtypes.py

@@ -282,13 +282,5 @@ def test_convert_string_dtype(self):
 
     def test_convert_bool_dtype(self):
         # GH32287
-        df = pd.DataFrame([["abc", 123, True]])
-        exp_dtypes = pd.Series([np.object, np.int64, np.bool])
-        tm.assert_series_equal(df.dtypes, exp_dtypes)
-
-        df_1 = df.convert_dtypes()
-        exp_dtypes_1 = pd.Series([pd.StringDtype(), pd.Int64Dtype(), pd.BooleanDtype()])
-        tm.assert_series_equal(df_1.dtypes, exp_dtypes_1)
-
-        df_2 = df_1.convert_dtypes()
-        tm.assert_series_equal(df_2.dtypes, exp_dtypes_1)
+        df = pd.DataFrame({"A": pd.array([True])})
+        tm.assert_frame_equal(df, df.convert_dtypes())