在Sklearn XGB API中，您不需要显式指定num_class参数。如果目标具有两个以上级别，则XGBClassifier会自动切换到多类分类模式。
evals_result = {}self.classes_ = list(np.unique(y))self.n_classes_ = len(self.classes_) if self.n_classes_ > 2: # Switch to using a multiclass objective in the underlying XGB instance xgb_options["objective"] = "multi:softprob" xgb_options['num_class'] = self.n_classes_在此处检查完整的源代码：https : //github.com/dmlc/xgboost/blob/master/python-
package/xgboost/sklearn.py
