如何从 pandas 数据框中获取不同的行？

Question

我无法从我的数据框中获取不同的值。下面是我目前使用的代码，第 25 行（vier() 的第 3 行）是问题所在：我想展示前 10 个最快的驱动程序基于他们的平均热度（卡丁车热度）时间。

输入：

HeatNumber,NumberOfKarts,KartNumber,DriverName,Laptime
334,11,5,Monique,00:53.862
334,11,5,Monique,00:59.070
334,11,5,Monique,00:47.832
334,11,5,Monique,00:47.213
334,11,5,Monique,00:51.975
334,11,5,Monique,00:46.423
334,11,5,Monique,00:49.539
334,11,5,Monique,00:49.935
334,11,5,Monique,00:45.267
334,11,12,Robert-Jan,00:55.606
334,11,12,Robert-Jan,00:52.249
334,11,12,Robert-Jan,00:50.965
334,11,12,Robert-Jan,00:53.878
334,11,12,Robert-Jan,00:48.802
334,11,12,Robert-Jan,00:48.766
334,11,12,Robert-Jan,00:46.003
334,11,12,Robert-Jan,00:46.257
334,11,12,Robert-Jan,00:47.334
334,11,20,Katja,00:56.222
334,11,20,Katja,01:01.005
334,11,20,Katja,00:50.296
334,11,20,Katja,00:48.004
334,11,20,Katja,00:51.203
334,11,20,Katja,00:47.672
334,11,20,Katja,00:50.243
334,11,20,Katja,00:50.453
334,11,20,Katja,01:06.192
334,11,13,Bensu,00:56.332
334,11,13,Bensu,00:54.550
334,11,13,Bensu,00:52.023
334,11,13,Bensu,00:52.518
334,11,13,Bensu,00:50.738
334,11,13,Bensu,00:50.359
334,11,13,Bensu,00:49.307
334,11,13,Bensu,00:49.595
334,11,13,Bensu,00:50.504
334,11,17,Marit,00:56.740
334,11,17,Marit,00:52.534
334,11,17,Marit,00:48.331
334,11,17,Marit,00:56.204
334,11,17,Marit,00:49.066
334,11,17,Marit,00:49.210
334,11,17,Marit,00:45.655
334,11,17,Marit,00:46.261
334,11,17,Marit,00:46.837
334,11,11,Niels,00:58.518
334,11,11,Niels,01:01.562
334,11,11,Niels,00:51.238
334,11,11,Niels,00:48.808

代码：

import pandas as pd
import matplotlib.pyplot as plt

#Data
df = pd.read_csv('dataset_kartanalyser.csv')
df = df.dropna(axis=0, how='any')
df = df.join(df['Laptime'].str.split(':', 1, expand=True).rename(columns={0:'M', 1:'S'}))
df['M'] = df['M'].astype(int)
df['S'] = df['S'].astype(float)
df['Laptime'] = (df['M'] * 60) + df['S']
df.drop(['M', 'S'], axis=1, inplace=True)

#Funties
def twee():
    print("Het totaal aantal karts = " + str(df['KartNumber'].nunique())) 
    print("Het aantal unique drivers = " + str(df['DriverName'].nunique()))
    print("Het totaal aantal heats = " + str(df['HeatNumber'].nunique())) 

def drie():
    print("De 10 snelste Drivers obv individuele tijd zijn: ")
    print((df.groupby('DriverName')['Laptime'].nsmallest(1)).nsmallest(10))

def vier():
    print('De 10 snelste Drivers obv snelste heat gemiddelde:')
    print((df.groupby(['DriverName', 'HeatNumber'])['Laptime'].mean().round(3)).nsmallest(10))

print(df)
     HeatNumber  NumberOfKarts KartNumber DriverName  Laptime
0           334             11          5    Monique   53.862
1           334             11          5    Monique   59.070
2           334             11          5    Monique   47.832
3           334             11          5    Monique   47.213
4           334             11          5    Monique   51.975
...         ...            ...        ...        ...      ...
4053        437              2         20       luuk   39.678
4054        437              2         20       luuk   39.872
4055        437              2         20       luuk   39.454
4056        437              2         20       luuk   39.575
4057        437              2         20       luuk   39.648

输出：

DriverName   HeatNumber
giovanni     411           26.233
ryan         411           27.747
giovanni     408           27.938
papa         394           28.075
guus         406           28.998
Rob          427           29.371
Suus         427           29.416
Jan-jullius  394           29.428
Joep         427           29.934
Indy         423           29.991

我得到的输出几乎是正确的，希望驱动程序“giovanni”出现两次。我只想显示每个车手最快的平均热身时间。有人知道怎么做吗？

Answer 1

ok 所以在像这样的列上添加 drop_duplication 只需要添加排序 df.sort_values('B', 升序=真)
.drop_duplicates('A', 保持='first')

(df.groupby(['DriverName', 'HeatNumber'])['Laptime'].mean().round(3)sort_values('Laptime', ascending=True).drop_duplicates('DriverName', keep='first')).nsmallest(10))

Answer 2

您按 Drivername 和 HeatNumber 对数据进行分组。查看 HeatNumbers，其中一个是 411，另一个是 408。因此 pandas 了解它们完全不同。如果你等于他们，他们就是一个。

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