'RandomForestClassifier' object has no attribute 'oob_score_ in python I am getting:

AttributeError: 'RandomForestClassifier' object has no attribute 'oob_score_'.
But I can see the attribute oob_score_ in sklearn random forest classifier documentation.

param = [10,15,20,25,30, 40]  
# empty list that will hold cv scores
cv_scores = []
# perform 10-fold cross validation
for i in tqdm(param):
    clf = RandomForestClassifier(n_estimators = i, max_depth = None,bootstrap = True, oob_score = True)
    scores = clf.oob_score_
    cv_scores.append(scores)


ERROR

AttributeError                            Traceback (most recent call last)
&lt;ipython-input-37-d6c9c54f299e&gt; in &lt;module&gt;()
     15 for i in tqdm(param):
     16     clf = RandomForestClassifier(n_estimators = i, max_depth = None,bootstrap = True, oob_score = True)
---&gt; 17     scores = clf.oob_score_
     18     cv_scores.append(scores)
     19 

AttributeError: 'RandomForestClassifier' object has no attribute 'oob_score_'
This kaggle guide explains Random Forest.

Setting warm_start to True might give you a solution to your problem. The default value is False.