def get_popularity_to_clickouts_ratio(df):
    indexes_list = explode(df[df["action_type"] == "clickout item"],"impressions")['impressions'].unique
    indexes_list.sort()
    df_clicks = df[df["action_type"] == "clickout item"]
    df_compared_indexes = pd.DataFrame(columns=(indexes_list))
    df_compared_indexes.index = indexes_list
    for col in df_compared_indexes.columns:
        df[col].values[:] = 0
    for index, row in df_compared_indexes.iterrows():
        impression_array = df['impressions'].apply(string_to_array)
        row = row.apply
    return df_compared_indexes