我在开始使用Kaggle时，正在进行一个指导任务，预测泰坦尼克号事故中谁生还了，谁没有生还。

我按照要求完成了所有步骤。

所以我的最后一个代码单元格看起来是这样的

from sklearn.ensemble import RandomForestClassifiery = train_data['Survived']features = ["Pclass","Sex","SibSp","Parch"]X = pd.get_dummies(train_data[features])X_test = pd.get_dummies(train_data[features])model = RandomForestClassifier(n_estimators=1,max_depth=5,random_state=1)model.fit(X,y)predictions = model.predict(X_test)output = pd.DataFrame({'PassengerId': test_data.PassengerId, 'Survived': predictions})output.to_csv('my_submission.csv', index=False)print("Your submission was successfully saved!")

编译后显示以下错误：

ValueError                                Traceback (most recent call last)<ipython-input-24-7d2fc2ea2973> in <module>     11      12 ---> 13 output = pd.DataFrame({'PassengerId': test_data.PassengerId, 'Survived': predictions})     14 output.to_csv('my_submission.csv', index=False)     15 print("Your submission was successfully saved!")/opt/conda/lib/python3.7/site-packages/pandas/core/frame.py in __init__(self, data, index, columns, dtype, copy)    433             )    434         elif isinstance(data, dict):--> 435             mgr = init_dict(data, index, columns, dtype=dtype)    436         elif isinstance(data, ma.MaskedArray):    437             import numpy.ma.mrecords as mrecords/opt/conda/lib/python3.7/site-packages/pandas/core/internals/construction.py in init_dict(data, index, columns, dtype)    252             arr if not is_datetime64tz_dtype(arr) else arr.copy() for arr in arrays    253         ]--> 254     return arrays_to_mgr(arrays, data_names, index, columns, dtype=dtype)    255     256 /opt/conda/lib/python3.7/site-packages/pandas/core/internals/construction.py in arrays_to_mgr(arrays, arr_names, index, columns, dtype)     62     # figure out the index, if necessary     63     if index is None:---> 64         index = extract_index(arrays)     65     else:     66         index = ensure_index(index)/opt/conda/lib/python3.7/site-packages/pandas/core/internals/construction.py in extract_index(data)    376                         f"length {len(index)}"    377                     )--> 378                     raise ValueError(msg)    379             else:    380                 index = ibase.default_index(lengths[0])ValueError: array length 891 does not match index length 418

然而，我无法调试出我的错误到底是什么，有人能帮我吗？谢谢你。

回答：

你构建X_test数据框的方式不正确，因为你使用的是train_data而不是test_data。这导致在创建输出文件时，test_data.PassengerId和predictions的大小不匹配。

修正以下这行代码，它就会工作：

X_test = pd.get_dummies(test_data[features])