python - 基于其他列用该列中的其他值填充 NaN 值

Question

我有一个像这样的熊猫数据框：

INPUT df:

Student_ID   Subject     Weekly_Feedback
100101         NaN         Excellent: 5
100101         NaN         very good:4
100101       Physics       Good: 3
100101         NaN         Excellent: 5
100102         NaN         Excellent: 5
100102       Chemistry     Good: 3
100102         NaN         Good: 3
100102         NaN         very Good: 3
100102         NaN         Needs improvement: 2

我想用对应的主题填充Subject列中具有NaN值的行Student_ID。

Expected OUTPUT df:

Student_ID   Subject     Weekly_Feedback
100101       Physics      Excellent: 5
100101       Physics      very good:4
100101       Physics      Good: 3
100101       Physics      Excellent: 5
100102       Chemistry    Excellent: 5
100102       Chemistry    Good: 3
100102       Chemistry    Good: 3
100102       Chemistry    very Good: 3
100102       Chemistry    Needs improvement: 2

标签： pythonpython-3.xpandasdataframeisnull