More on Pipelines — Applied Machine Learning in Python

param_grid = [ # list of two dicts
    # first dict always uses MinMaxScaler
    {'scaler': [MinMaxScaler()],
     # two options for feature_range:
     'feature_range': [(0, 1), (-1, 1)]},
    # second dict always uses StandardScaler
    # there are no options that we're tuning
    {'scaler': [StandardScaler()]}   
]