Fix EmptyDataError when reading empty CSV files

Handle pandas.errors.EmptyDataError that occurs when pd.read_csv() encounters an existing but empty CSV file. This fix catches the error in both 'append' and 'update' modes and treats the empty file as if it doesn't exist, creating a new file with the current data.

The fix prevents crashes when emission CSV files exist but are empty, which can happen if a previous write operation was interrupted.

Added test cases for both append and update modes with empty files.

Author: isztldav

codecarbon/output_methods/file.py

@@ -96,14 +96,30 @@ def out(self, total: EmissionsData, _):
         if not file_exists:
             df = new_df
         elif self.on_csv_write == "append":
-            df = pd.read_csv(self.save_file_path)
+            try:
+                df = pd.read_csv(self.save_file_path)
+            except pd.errors.EmptyDataError:
+                logger.warning(
+                    f"File {self.save_file_path} exists but is empty. Creating new file."
+                )
+                df = new_df
+                df.to_csv(self.save_file_path, index=False)
+                return
             # Filter out empty or all-NA columns, to avoid warnings from Pandas,
             # see https://github.com/pandas-dev/pandas/issues/55928
             df = df.dropna(axis=1, how="all")
             new_df = new_df.dropna(axis=1, how="all")
             df = pd.concat([df, new_df])
         else:
-            df = pd.read_csv(self.save_file_path)
+            try:
+                df = pd.read_csv(self.save_file_path)
+            except pd.errors.EmptyDataError:
+                logger.warning(
+                    f"File {self.save_file_path} exists but is empty. Creating new file."
+                )
+                df = new_df
+                df.to_csv(self.save_file_path, index=False)
+                return
             df_run = df.loc[df.run_id == total.run_id]
             if len(df_run) < 1:
                 df = pd.concat([df, new_df])

tests/output_methods/test_file.py

@@ -173,6 +173,30 @@ def test_file_output_out_update_file_exists_one_matchingrows(self):
     #     file_output = FileOutput("test.csv", self.temp_dir, on_csv_write="append")
     #     file_output.out(self.emissions_data, None)
 
+    def test_file_output_out_append_empty_file_exists(self):
+        file_output = FileOutput("test.csv", self.temp_dir, on_csv_write="append")
+        # Create an empty file
+        with open(file_output.save_file_path, "w") as _:
+            pass
+
+        # This should not raise an error
+        file_output.out(self.emissions_data, None)
+
+        df = pd.read_csv(os.path.join(self.temp_dir, "test.csv"))
+        self.assertEqual(len(df), 1)
+
+    def test_file_output_out_update_empty_file_exists(self):
+        file_output = FileOutput("test.csv", self.temp_dir, on_csv_write="update")
+        # Create an empty file
+        with open(file_output.save_file_path, "w") as _:
+            pass
+
+        # This should not raise an error
+        file_output.out(self.emissions_data, None)
+
+        df = pd.read_csv(os.path.join(self.temp_dir, "test.csv"))
+        self.assertEqual(len(df), 1)
+
     def test_file_output_task_out(self):
         task_emissions_data = [
             TaskEmissionsData(