m.addConstrs((quicksum(X_rdc_to_dist[j,i,s,t] for j in rdc_list) == demand_fcst_df.loc[(demand_fcst_df['ADDR_BOOK_N'] == i)&
                                           (demand_fcst_df['SKU'] == s)&
                                           (demand_fcst_df['DATE'] == t),'CASES'].sum())
             for i in dist_list
             for s in sku_list
             for t in time_periods_list
             )

len(rdc_list) = 10
len(cdc_list) = 5
len(sku_list) = 20
len(dist_list) = 1333
len(time_period_list) = 100