Python 如何有条件地更新 Pandas 中的 DataFrame 列
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How to conditionally update DataFrame column in Pandas
提问by TravisVOX
With this DataFrame, how can I conditionally set ratingto 0 when line_raceis equal to zero?
使用此 DataFrame，如何rating在line_race等于0 时有条件地设置为 0 ？
line_track line_race rating foreign
25 MTH 10 84 False
26 MTH 6 88 False
27 TAM 5 87 False
28 GP 2 86 False
29 GP 7 59 False
30 LCH 0 103 True
31 LEO 0 125 True
32 YOR 0 126 True
33 ASC 0 124 True
In other words, what is the proper way on a DataFrame to say if ColumnA = x then ColumnB = y else ColumnB = ColumnB
换句话说，如果 ColumnA = x then ColumnB = y else ColumnB = ColumnB，那么在 DataFrame 上的正确方法是什么
采纳答案by Viktor Kerkez
df.loc[df['line_race'] == 0, 'rating'] = 0
回答by SpeedCoder5
Use numpy.whereto say if ColumnA = x then ColumnB = y else ColumnB = ColumnB:
使用numpy.where说if ColumnA = x then ColumnB = y else ColumnB = ColumnB：
df['rating'] = np.where(df['line_race']==0, 0, df['rating'])
