pandas set_value用法

原始代碼：

df_valid_inventory_sel_tmp['col1']=-9999
for index in df_valid_inventory_sel_tmp.index:
    time_stamp = time.time()
    df_valid_inventory_sel_tmp['col1'][index] =su.sta_mean(index)  ##傳統拷貝 40ms
    #df_valid_inventory_sel_tmp.set_value(index,'mean_lasteN',su.sta_mean(index)) ##優化賦值,10ms以內
    print(str(time.time() - time_stamp))

報“Warning”： A value is trying to be set on a copy of a slice from a DataFrame

  優化後代碼：

#df_valid_inventory_sel_tmp['col1']=-9999
for index in df_valid_inventory_sel_tmp.index:
    time_stamp = time.time()
   #df_valid_inventory_sel_tmp['col1'][index] =su.sta_mean(index)  ##傳統拷貝 40ms
    df_valid_inventory_sel_tmp.set_value(index,'mean_lasteN',su.sta_mean(index)) ##優化賦值,10ms以內
    print(str(time.time() - time_stamp))

用set_value比直接賦值快4倍左右