searchgrid.py 文件源码

def make_union(*transformers, **kwargs):
    """Construct a FeatureUnion with alternative estimators to search over

    Parameters
    ----------
    steps
        Each step is specified as one of:

        * an estimator instance
        * None (meaning no features)
        * a list of the above, indicating that a grid search should alternate
          over the estimators (or None) in the list
    kwargs
        Keyword arguments to the constructor of
        :class:`sklearn.pipeline.FeatureUnion`.

    Notes
    -----
    Each step is named according to the set of estimator types in its list:

    * if a step has only one type of estimator (disregarding None), it takes
      that estimator's class name (lowercased)
    * if a step has estimators of mixed type, the step is named 'alt'
    * if there are multiple steps of the same name using the above rules,
      a suffix '-1', '-2', etc. is added.
    """
    steps, grid = _name_steps(transformers)
    return set_grid(_FeatureUnion(steps, **kwargs), **grid)