我想知道如何保存之前的結果，該結果與后面的每一行中的某些條件（df['condition']）相匹配。我知道如何使用 for 循環來做到這一點，但我知道在使用 pandas 時應該避免它們。下面是一個例子。列 df['desired_result] 代表我想要實現的目標。import pandas as pdimport numpy as npdates = pd.date_range('1/1/2000', periods=10)values = np.arange(10.0, 20.0, 1.0)data = {'date': dates, 'value': values}df = pd.DataFrame.from_dict(data)df['condition'] = [False, False, True, True, False, True, False, False, True, False]df_valid = df[df['condition']]df['desired_result'] = [np.nan, np.nan, 12, 13, 13, 15, 15, 15, 18, 18]
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素胚勾勒不出你
TA貢獻1827條經驗 獲得超9個贊
# use df.where based on your condition and assign it to a new col
# Anywhere column condition is True return the value else return NaN
# then add ffill to forward fill NaN values
df['r'] = df['value'].where(df['condition'] == True, np.nan).ffill()
date value condition desired_result r
0 2000-01-01 10.0 False NaN NaN
1 2000-01-02 11.0 False NaN NaN
2 2000-01-03 12.0 True 12.0 12.0
3 2000-01-04 13.0 True 13.0 13.0
4 2000-01-05 14.0 False 13.0 13.0
5 2000-01-06 15.0 True 15.0 15.0
6 2000-01-07 16.0 False 15.0 15.0
7 2000-01-08 17.0 False 15.0 15.0
8 2000-01-09 18.0 True 18.0 18.0
9 2000-01-10 19.0 False 18.0 18.0
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