python - Pandas ，将系列连接到 DF 作为行

Question

我试图将一个系列添加到一个空的 DataFrame 中，但找不到答案 在文档或其他问题中。因为您可以按行附加两个 DataFrame 或者按列看来系列中必须缺少一个“轴标记”。能 谁能解释为什么这不起作用？

import Pandas as pd
df1 = pd.DataFrame()
s1 = pd.Series(['a',5,6])
df1 = pd.concat([df1,s1],axis = 1)
#go run some process return s2, s3, sn ...
s2 = pd.Series(['b',8,9])
df1 = pd.concat([df1,s2],axis = 1)
s3 = pd.Series(['c',10,11])
df1 = pd.concat([df1,s3],axis = 1)

If my example above is some how misleading perhaps using the example from the docs will help.

Quoting: Appending rows to a DataFrame.
While not especially efficient (since a new object must be created), you can append a single row to a DataFrame by passing a Series or dict to append, which returns a new DataFrame as above. End Quote.

The example from the docs appends "S", which is a row from a DataFrame, "S1" is a Series and attempting to append "S1" produces an error. My question is WHY will appending "S1 not work? The assumption behind the question is that a DataFrame must code or contain axes information for two axes, where a Series must contain only information for one axes.

df = pd.DataFrame(np.random.randn(8, 4), columns=['A','B','C','D'])
s = df.xs(3); #third row of DataFrame
s1 = pd.Series([np.random.randn(4)]); #new Series of equal len
df= df.append(s, ignore_index=True)

结果

   0  1

0  a  b

1  5  8

2  6  9

想要的

   0  1 2

0  a  5 6

1  b  8 9

Answer 1

你很接近，只是转置了 concat

的结果

In [14]: s1
Out[14]: 
0    a
1    5
2    6
dtype: object

In [15]: s2
Out[15]: 
0    b
1    8
2    9
dtype: object

In [16]: pd.concat([s1, s2], axis=1).T
Out[16]: 
   0  1  2
0  a  5  6
1  b  8  9

[2 rows x 3 columns]

您也不需要创建空的 DataFrame。