#!/usr/bin/env python
# encoding: utf-8


def column_values_to_column(pivot_column, value_column, kept_columns, df):
    """Pivot_column's values go to column with value_column under it, keeping kept_columns

    :param pivot_column: column name where value will become columns
    :param value_column: column name where value will be under pivot_column
    :param kept_columns: unchanged columns
    :param df: DataFrame to work with

    :return: Stack dataframe

    """
    if pivot_column in kept_columns:
        pivot_columns = kept_columns
    else:
        pivot_columns = kept_columns + [pivot_column]

    return df.set_index(pivot_columns).unstack(pivot_column)[value_column].reset_index()