在使用 pandas 進行資料分析的過程中,我們常常會遇到將一行資料展開成多行的需求,多麼希望能有一個類似於 hive sql 中的 explode 函式。
這個函式如下:
Code
# !/usr/bin/env python # -*- coding:utf-8 -*- # create on 18/4/13 import pandas as pd def dataframe_explode(dataframe, fieldname): temp_fieldname = fieldname + '_made_tuple_' dataframe[temp_fieldname] = dataframe[fieldname].apply(tuple) list_of_dataframes = [] for values in dataframe[temp_fieldname].unique().tolist(): list_of_dataframes.append(pd.DataFrame({ temp_fieldname: [values] * len(values), fieldname: list(values), })) dataframe = dataframe[list(set(dataframe.columns) - set([fieldname]))].merge(pd.concat(list_of_dataframes), how='left', on=temp_fieldname) del dataframe[temp_fieldname] return dataframe df = pd.DataFrame({'listcol':[[1,2,3],[4,5,6]], "aa": [222,333]}) df = dataframe_explode(df, "listcol")
Description
將 dataframe 按照某一指定列進行展開,使得原來的每一行展開成一行或多行。( 註:該列可迭代, 例如list, tuple, set)
補充知識:Pandas列中的字典/列表拆分為單獨的列
我就廢話不多說了,大家還是直接看程式碼吧
[1] df Station ID Pollutants 8809 {"a": "46", "b": "3", "c": "12"} 8810 {"a": "36", "b": "5", "c": "8"} 8811 {"b": "2", "c": "7"} 8812 {"c": "11"} 8813 {"a": "82", "c": "15"}
Method 1:
step 1: convert the Pollutants column to Pandas dataframe series
df_pol_ps = data_df['Pollutants'].apply(pd.Series) df_pol_ps: a b c 0 46 3 12 1 36 5 8 2 NaN 2 7 3 NaN NaN 11 4 82 NaN 15
step 2: concat columns a, b, c and drop/remove the Pollutants
df_final = pd.concat([df, df_pol_ps], axis = 1).drop('Pollutants', axis = 1) df_final: StationID a b c 0 8809 46 3 12 1 8810 36 5 8 2 8811 NaN 2 7 3 8812 NaN NaN 11 4 8813 82 NaN 15
Method 2:
df_final = pd.concat([df, df['Pollutants'].apply(pd.Series)], axis = 1).drop('Pollutants', axis = 1) df_final: StationID a b c 0 8809 46 3 12 1 8810 36 5 8 2 8811 NaN 2 7 3 8812 NaN NaN 11 4 8813 82 NaN 15
[zhang3221994 ] pandas dataframe 中的explode函式用法詳解已經有241次圍觀