updated to use f string formatting

use-cases/text-to-image-fine-tuning/code/train

@@ -24,10 +24,13 @@ def train():
     try:
         input_files = [ os.path.join(training_path, file) for file in os.listdir(training_path) ]
         if len(input_files) == 0:
-            raise ValueError(('There are no files in {}.\n' +
-                              'This usually indicates that the channel ({}) was incorrectly specified,\n' +
-                              'the data specification in S3 was incorrectly specified or the role specified\n' +
-                              'does not have permission to access the data.').format(training_path, channel_name))
+            error_message = (
+                f"There are no files in {training_path}.\n"
+                f"This usually indicates that the channel ({channel_name}) was incorrectly specified,\n"
+                "the data specification in S3 was incorrectly specified or the role specified\n"
+                "does not have permission to access the data."
+            )
+            raise ValueError(error_message)
 
         # Call the program that was installed in the training container, which uses the kohya-ss libraries to train
         # Stable Diffusion XL given the kohya-sdxl-config.toml file that is present in the training S3 bucket
@@ -44,11 +47,14 @@ def train():
         print('Training complete.')
     except Exception as e:
         # Write out an error file. This will be returned as the failureReason in the DescribeTrainingJob result
-        trc = traceback.format_exc()
-        with open(os.path.join(output_path, 'failure'), 'w') as s:
-            s.write('Exception during training: ' + str(e) + '\n' + trc)
+        traceback_str = traceback.format_exc()
+        failure_log_path = os.path.join(output_path, 'failure')
+
+        with open(failure_log_path, 'w') as log_file:
+            log_file.write(f'Exception during training: {str(e)}\n{traceback_str}')
         # Printing this causes the exception to be in the training job logs, as well.
-        print('Exception during training: ' + str(e) + '\n' + trc, file=sys.stderr)
+        print(f'Exception during training: {str(e)}\n{traceback_str}', file=sys.stderr)
+
         # A non-zero exit code causes the training job to be marked as Failed.
         sys.exit(255)