python-2.7 - KeyError : in pandas when trying to change boolean column values into string while using . loc方法

Question

我正在运行一个条件循环，根据“单独”列的值在我的 DataFrame (TDF) 中创建一个新列。如果值为 0，则添加字符串“alone”，否则在“alone”列中添加“with family”。我正在使用代码:我收到错误:

tdf['alone'].loc[['alone'] >0]= 'with family'
tdf['alone'].loc[['alone'] ==0] = 'alone'

运行上述行后，我收到以下错误:

KeyError: 'cannot use a single bool to index into setitem'

我提到了这个same question ，我收集到的是我需要 row_indexer在tdf['alone'].loc[[row_indexer,['alone']] = 'alone'但我不知道如何获取 row_indexer 中的值

Answer 1

pandas.Series.clip

将值剪辑为仅 0 和 1 并用它来切片数组

tdf.assign(alone=np.array(['alone', 'with family'])[tdf.alone.clip(0, 1)])

         alone  col
0  with family    1
1  with family    1
2  with family    9
3        alone    4
4  with family    2
5        alone    3

---

pandas.Series.map

tdf.assign(alone=tdf.alone.map(lambda x: 'with family' if x else 'alone'))

         alone  col
0  with family    1
1  with family    1
2  with family    9
3        alone    4
4  with family    2
5        alone    3

---

map

版本 2

tdf.assign(alone=tdf.alone.map(lambda x: {0: 'alone'}.get(x, 'with family')))

         alone  col
0  with family    1
1  with family    1
2  with family    9
3        alone    4
4  with family    2
5        alone    3

---

设置

借自@jezrael

tdf = pd.DataFrame({'alone':[4,4,5,0,5,0],
                   'col':[1,1,9,4,2,3]})