[{'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:#One Hot Encoding columns\ndef one_hot(df, cols):\n    """\n    @param df pandas DataFrame\n    @param cols a list of columns to encode \n    @return a DataFrame with one-hot encoding\n    """\n    i = 0\n    for each in cols:\n        #print (each)\n        dummies = pd.get_dummies(df[each], prefix=each, drop_first= True)\n        if i == 0: \n            print (dummies)\n            i = i + 1\n        df = pd.concat([df, dummies], axis=1)\n    return df'}, {'role': 'assistant', 'content': 'data_preprocessing'}]