Invalid parameter for sklearn estimator pipeline

Question

I am implementing an example from the O\'Reilly book \"Introduction to Machine Learning with Python\", using Python 2.7 and sklearn 0.16.

The code I am using:

Answer 1

Note that if you are using a pipeline with a voting classifier and a column selector, you will need multiple layers of names:

pipe1 = make_pipeline(ColumnSelector(cols=(0, 1)),
                      LogisticRegression())
pipe2 = make_pipeline(ColumnSelector(cols=(1, 2, 3)),
                      SVC())
votingClassifier = VotingClassifier(estimators=[
        ('p1', pipe1), ('p2', pipe2)])

You will need a param grid that looks like the following:

param_grid = { 
        'p2__svc__kernel': ['rbf', 'poly'],
        'p2__svc__gamma': ['scale', 'auto'],
    }

p2 is the name of the pipe and svc is the default name of the classifier you create in that pipe. The third element is the parameter you want to modify.

Answer 2

There should be two underscores between estimator name and it's parameters in a Pipeline logisticregression__C. Do the same for tfidfvectorizer

See the example at http://scikit-learn.org/stable/auto_examples/plot_compare_reduction.html#sphx-glr-auto-examples-plot-compare-reduction-py