python - Pandas DataFrame 不会重新索引和转置，返回 NaN

Question

我正在将 .csv 中的前 9 行读取到 DataFrame 中，它工作正常:

invoice_desc = pd.read_csv('path', sep=',', nrows = 9, header=None)

打印时，DataFrame 看起来像这样:

                  0                              1
0          Bill to                        /client/
1        Billing ID            xxxx-xxxx-xxxx-xxxx
2    Invoice number                     3359680287
3        Issue date                    31-Jan-2016
4          Due Date                    01-Mar-2016
5          Currency                           CURR
6  Invoice subtotal                   9,999,999.90
7          VAT (0%)                           0.00
8        Amount due                   9,999,999.90

我现在需要挑选某些行，重新索引并转置，以便我可以通过 to_sql() 将其插入 MySQL 数据库:

i = ['invoiceNum', 'issueDate', 'dueDate', 'invoiceSubtotal']
invoice_desc2 = pd.DataFrame(invoice_desc.loc[[2, 3, 4, 8],], index = i)
invoice_desc2.transpose()

print invoice_desc2

但是，该代码片段会重新索引，但不会保留值，并在打印时生成以下输出:

                   0    1
invoiceNum       NaN  NaN
issueDate        NaN  NaN
dueDate          NaN  NaN
invoiceSubtotal  NaN  NaN

我一直在阅读有关 Pandas 索引和切片的文章 here但我就是无法让它发挥作用。我究竟做错了什么？谢谢!

Answer 1

我认为您可以首先通过 loc 选择 invoice_desc 的子集，将其转置为 T然后按 i 更改列。不需要通过 pd.DataFrame 创建新的 DataFrame。

print invoice_desc
                  0                    1
0           Bill to             \tclient
1        Billing ID  xxxx-xxxx-xxxx-xxxx
2    Invoice number           3359680287
3        Issue date          31-Jan-2016
4          Due Date          01-Mar-2016
5          Currency                 CURR
6  Invoice subtotal         9,999,999.90
7          VAT (0%)                 0.00
8        Amount due         9,999,999.90

invoice_desc2 = invoice_desc.loc[[2, 3, 4, 8],:]
invoice_desc2 = invoice_desc2.T
print invoice_desc2
                2            3            4             8
0  Invoice number   Issue date     Due Date    Amount due
1      3359680287  31-Jan-2016  01-Mar-2016  9,999,999.90

i = ['invoiceNum', 'issueDate', 'dueDate', 'invoiceSubtotal']
invoice_desc2.columns = i
print invoice_desc2
       invoiceNum    issueDate      dueDate invoiceSubtotal
0  Invoice number   Issue date     Due Date      Amount due
1      3359680287  31-Jan-2016  01-Mar-2016    9,999,999.90

或者先通过i设置index，然后转置:

print invoice_desc
                  0                    1
0           Bill to             \tclient
1        Billing ID  xxxx-xxxx-xxxx-xxxx
2    Invoice number           3359680287
3        Issue date          31-Jan-2016
4          Due Date          01-Mar-2016
5          Currency                 CURR
6  Invoice subtotal         9,999,999.90
7          VAT (0%)                 0.00
8        Amount due         9,999,999.90

invoice_desc2 = invoice_desc.loc[[2, 3, 4, 8],:]
i = ['invoiceNum', 'issueDate', 'dueDate', 'invoiceSubtotal']
invoice_desc2.index = i
print invoice_desc2
                              0             1
invoiceNum       Invoice number    3359680287
issueDate            Issue date   31-Jan-2016
dueDate                Due Date   01-Mar-2016
invoiceSubtotal      Amount due  9,999,999.90

print invoice_desc2.T
       invoiceNum    issueDate      dueDate invoiceSubtotal
0  Invoice number   Issue date     Due Date      Amount due
1      3359680287  31-Jan-2016  01-Mar-2016    9,999,999.90