Unbalanced multiclass classification within Scikit.learn pipeline



I am using XGBClassifier to model an unbalanced multiclass target. I have a few questions:

  • First I would like to now where should I use the parameter weight=: on the instantion of the classifier or on the fit step of the pipeline?

  • Second question is how I calculate a weights. I assume that the sum of the array should be 1.

  • Third: Is there any order of the weight array that maps the diferent label classes?

Thank you all in advance