# Perform grid search to find optimal hyperparameters param_grid = {'n_estimators': 200, 'learning_rate': 0.5 'base_estimator__max_depth': 4 } grid_search = GridSearchCV(adaboost_clf, param_grid=param_grid, cv=5) grid_search.fit(X_train, y_train) adaboost_clf = grid_search.best_estimator_Input In [30] 'base_estimator__max_depth': 4 } ^ SyntaxError: invalid syntax

在这个例子中，你需要在`learning_rate`的值和`base_estimator__max_depth`之间添加一个逗号，因为它们是字典中的两个不同的键值对。缺少逗号可能会导致Python无法正确解析代码，并抛出SyntaxError异常。以下是正确的代码：

# Perform grid search to find optimal hyperparameters
param_grid = {'n_estimators': 200,
              'learning_rate': 0.5,
              'base_estimator__max_depth': 4 }
grid_search = GridSearchCV(adaboost_clf, param_grid=param_grid, cv=5)
grid_search.fit(X_train, y_train)
adaboost_clf = grid_search.best_estimator

这里我们将`learning_rate`和`base_estimator__max_depth`之间添加了逗号，这样Python就可以正确解析代码了。