当您使用带有网格搜索的嵌套估计器时，您可以使用 __ 作为分隔符来限定参数。在这种情况下，LogisticRegression 模型存储为 OneVsRestClassifier 模型中名为 estimator 的属性：

from sklearn.model_selection import GridSearchCV
from sklearn.linear_model import LogisticRegression
from sklearn.multiclass import OneVsRestClassifier

tuned_parameters = [{'estimator__C': [100, 10, 1, 0.1, 0.01, 0.001, 0.0001]}]

# Find Optimal C by grid search 

log_reg_clf = OneVsRestClassifier(LogisticRegression())

logistic_gs = GridSearchCV(log_reg_clf, tuned_parameters,scoring = 'f1_micro', cv=3)

logistic_gs.fit(x_train_bow, y_train)
print(logistic_gs.best_estimator_)

您可以看到我在这里使用 GridSearchCV、tf-idf、Logistic Regression 和 OneVsRestClassifier 设置了一个基本管道。在 param_grid 中，您可以设置'clf__estimator__C'而不仅仅是'C'

import numpy as np
from sklearn.feature_extraction.text import TfidfVectorizer
from sklearn.multiclass import OneVsRestClassifier
from sklearn.linear_model import LogisticRegression
from sklearn.model_selection import GridSearchCV
from sklearn.pipeline import Pipeline

tfidf_vectorizer = TfidfVectorizer(smooth_idf=True)

log_reg_clf = OneVsRestClassifier(
  estimator=LogisticRegression(
    intercept_scaling=1,
    class_weight='balanced',
    random_state=0
  )
)

# Create regularization hyperparameter space
C = np.logspace(0, 4, 10)

param_grid = [{
  'vect__ngram_range': [(1, 1), (1, 2), (1, 3), (1, 4)],
  'vect__max_features': (None, 5000, 10000, 50000),
  'vect__norm': ['l1','l2'],
  'clf__estimator__C': C,
  'clf__estimator__penalty': ['l1','l2']
}]

log_reg_clf_tfidf = Pipeline([
  ('vect', tfidf_vectorizer),
  ('clf', log_reg_clf)
])

print(log_reg_clf_tfidf.get_params().keys())

gs_logReg_tfidf = GridSearchCV(
  log_reg_clf_tfidf,
  param_grid,
  scoring='accuracy',
  cv=5,
  verbose=1,
  n_jobs=-1
)
gs_logReg_tfidf.fit(X_train, y_train)
print("The best parameters: \n", gs_logReg_tfidf.best_params_)
print("The best score: \n", gs_logReg_tfidf.best_score_)

df_test_predicted_idf = gs_logReg_tfidf.predict(X_test)