Scikit-Learn Decision Tree: Probability of prediction being a or b?

You can do something like the following:

from sklearn import tree

#load data
X = [[65,9],[67,7],[70,11],[62,6],[60,7],[72,13],[66,10],[67,7.5]]
Y=["male","female","male","female","female","male","male","female"]

#build model
clf = tree.DecisionTreeClassifier()

#fit
clf.fit(X, Y)

#predict
prediction = clf.predict([[68,9],[66,9]])

#probabilities
probs = clf.predict_proba([[68,9],[66,9]])

#print the predicted gender
print(prediction)
print(probs)

Theory

The result of clf.predict_proba(X) is: The predicted class probability which is the fraction of samples of the same class in a leaf.

Interpretation of the results:

The first print returns ['male' 'male'] so the data [[68,9],[66,9]] are predicted as males.

The second print returns:

[[ 0. 1.] [ 0. 1.]]

This means that the data were predicted as males and this is reported by the ones in the second column.

To see the order of the classes use: clf.classes_

This returns: ['female', 'male']