Pandas 数据透视表不返回值

Question

我有一个熊猫数据frame

df

，看起来像这样。

import pandas as pd
url = "https://www-genesis.destatis.de/genesisWS/rest/2020/data/tablefile?username=DEB924AL95&password=P@ssword1234&name=42153-0002&area=all&compress=false&transpose=false&startyear=1900&endyear=&timeslices=&regionalvariable=&regionalkey=&classifyingvariable1=WERT03&classifyingkey1=BV4TB&classifyingvariable2=WZ08V2&classifyingkey2=&classifyingvariable3=&classifyingkey3=&format=xlsx&job=false&stand=01.01.1970&language=en"

df = pd.read_excel(url, engine='openpyxl')

df = df.iloc[5:-3]
df.columns = ['Variable', 'Date', 'Value']
m = df['Date'].isna()

df['Date'] += '-' + df['Variable'].ffill()
df['Variable'] = df['Variable'].where(m).ffill()

df

import numpy as np
# Reshape your dataframe
out = (df[~m].replace('...', np.nan)
             .pivot_table(index='Date', columns='Variable',
                          values='Value', sort=False)
             .reset_index().rename_axis(columns=None))

out

这只给了我一个

Date

列，没有任何值。

    Date
0   January-1991
1   February-1991
2   March-1991
3   April-1991

我需要做哪些改变才能使其发挥作用？

Answer 1

问题是您

pivot_table

进行了数值聚合（默认为

mean

），但您的数据不是数字。首先使用

to_numeric

进行转换：

out = (df[~m].assign(Value=lambda d: pd.to_numeric(d['Value'], errors='coerce'))
             .pivot_table(index='Date', columns='Variable',
                          values='Value', sort=False)
             .reset_index().rename_axis(columns=None)
       )

输出摘录：

               Date  WZ08-05 Mining of coal and lignite  WZ08-06 Extraction of crude petroleum and natural gas  WZ08-08 Other mining and quarrying  WZ08-09 Mining support service activities  \
0      January-1991                               415.7                                              186.6                                   113.8                                      358.6   
1     February-1991                               409.6                                              187.7                                   114.6                                      360.3   
2        March-1991                               402.8                                              188.6                                   115.5                                      361.0   
3        April-1991                               397.0                                              189.6                                   116.6                                      361.3   
4          May-1991                               391.1                                              190.7                                   117.7                                      361.8   
..              ...                                 ...                                                ...                                     ...                                        ...   
388        May-2023                                26.2                                               61.5                                    88.2                                       60.7   
389       June-2023                                25.2                                               60.8                                    87.4                                       66.6   
390       July-2023                                24.3                                               60.1                                    86.7                                       72.5   
391     August-2023                                23.4                                               59.5                                    85.9                                       78.1   
392  September-2023                                22.4                                               58.7                                    85.2                                       83.8