如何在 pandas 中合并/合并列?

问题描述

我有一个(示例)数据框，其中包含4列:

I have a (example-) dataframe with 4 columns:

data = {'A': ['a', 'b', 'c', 'd', 'e', 'f'],
    'B': [42, 52, np.nan, np.nan, np.nan, np.nan],
    'C': [np.nan, np.nan, 31, 2, np.nan, np.nan],
    'D': [np.nan, np.nan, np.nan, np.nan, 62, 70]}
df = pd.DataFrame(data, columns = ['A', 'B', 'C', 'D'])

    A   B       C       D
0   a   42.0    NaN     NaN
1   b   52.0    NaN     NaN
2   c   NaN     31.0    NaN
3   d   NaN     2.0     NaN
4   e   NaN     NaN     62.0
5   f   NaN     NaN     70.0

我现在想将B，C和D列合并/合并到新的E列，如本例所示:

I would now like to merge/combine columns B, C, and D to a new column E like in this example:

data2 = {'A': ['a', 'b', 'c', 'd', 'e', 'f'],
    'E': [42, 52, 31, 2, 62, 70]}
df2 = pd.DataFrame(data2, columns = ['A', 'E'])

    A   E
0   a   42
1   b   52
2   c   31
3   d   2
4   e   62
5   f   70

我在此处发现了一个非常相似的问题，但这在列A的末尾添加合并的列B，C和D:

I found a quite similar question here but this adds the merged colums B, C, and D at the end of column A:

0      a
1      b
2      c
3      d
4      e
5      f
6     42
7     52
8     31
9      2
10    62
11    70
dtype: object

感谢您的帮助.

推荐答案

选项1
使用assign和drop

Option 1
Using assign and drop

In [644]: cols = ['B', 'C', 'D']

In [645]: df.assign(E=df[cols].sum(1)).drop(cols, 1)
Out[645]:
   A     E
0  a  42.0
1  b  52.0
2  c  31.0
3  d   2.0
4  e  62.0
5  f  70.0

---

选项2
使用赋值和drop

---

Option 2
Using assignment and drop

In [648]: df['E'] = df[cols].sum(1)

In [649]: df = df.drop(cols, 1)

In [650]: df
Out[650]:
   A     E
0  a  42.0
1  b  52.0
2  c  31.0
3  d   2.0
4  e  62.0
5  f  70.0

---

选项3 最近，我喜欢第3个选项.
使用groupby

---

Option 3 Lately, I like the 3rd option.
Using groupby

In [660]: df.groupby(np.where(df.columns == 'A', 'A', 'E'), axis=1).first() #or sum max min
Out[660]:
   A     E
0  a  42.0
1  b  52.0
2  c  31.0
3  d   2.0
4  e  62.0
5  f  70.0

In [661]: df.columns == 'A'
Out[661]: array([ True, False, False, False], dtype=bool)

In [662]: np.where(df.columns == 'A', 'A', 'E')
Out[662]:
array(['A', 'E', 'E', 'E'],
      dtype='|S1')

这篇关于如何在 pandas 中合并/合并列?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！