scikit dummy: Training a DummyClassifier
A dummy classifier works just like any other scikit-learn estimator.
from sklearn.dummy import DummyClassifier
mod = DummyClassifier(strategy="most_frequent")
mod.fit(X, y)
The benefit of this model is that it really meant as a "dumb"-model. If this model performs nearly as well as your best model ... then you know you something is up.