[{'role': 'system', 'content': "You are an expert in machine learning and your task is to classify code snippets into one of the following categories: ['helper_functions', 'load_data', 'data_exploration', 'data_preprocessing', 'evaluation', 'modelling', 'prediction', 'result_visualization', 'save_results', 'comment_only']."}, {'role': 'user', 'content': "Identify the single most appropriate category to which the provided code belongs. Provide your response as a single category label without any additional information, commentary, or personal opinions.\\nPython Code:for year in years:\npath = r'/Users/Harish/Documents/HK_Work/Python/Python-for-Data-Analysis/chapter 02/names/yob%d.txt' % year\nframe = pd.read_csv(path, names=columns)\nframe['year'] = year\npieces.append(frame)"}, {'role': 'assistant', 'content': 'data_preprocessing'}]