pandas 无法按熊猫数据框中的时间戳编制索引
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Can't index by timestamp in pandas dataframe
提问by Delta_Fore
I took an excel sheet which has dates and some values and want to convert them to pandas dataframe and select only rows which are between certain dates.
我拿了一个包含日期和一些值的 excel 表，并希望将它们转换为 Pandas 数据框并只选择特定日期之间的行。
For some reason I cannot select a row by date index
由于某种原因，我无法按日期索引选择一行
Raw Data in Excel file
Excel 文件中的原始数据
MCU
Timestamp 50D 10P1 10P2 10P3 10P6 10P9 10P12
12-Feb-15 25.17 5.88 5.92 5.98 6.18 6.23 6.33
11-Feb-15 25.9 6.05 6.09 6.15 6.28 6.31 6.39
10-Feb-15 26.38 5.94 6.05 6.15 6.33 6.39 6.46
Code
代码
xls = pd.ExcelFile('e:/Data.xlsx')
vols = xls.parse(asset.upper()+'VOL',header=1)
vols.set_index('Timestamp',inplace=True)
Data before set_index
set_index 之前的数据
Timestamp 50D 10P1 10P2 10P3 10P6 10P9 10P12 25P1 25P2 \
0 2015-02-12 25.17 5.88 5.92 5.98 6.18 6.23 6.33 2.98 3.08
1 2015-02-11 25.90 6.05 6.09 6.15 6.28 6.31 6.39 3.12 3.17
2 2015-02-10 26.38 5.94 6.05 6.15 6.33 6.39 6.46 3.01 3.16
Data after set_index
set_index 后的数据
50D 10P1 10P2 10P3 10P6 10P9 10P12 25P1 25P2 25P3 \
Timestamp
2015-02-12 25.17 5.88 5.92 5.98 6.18 6.23 6.33 2.98 3.08 3.21
2015-02-11 25.90 6.05 6.09 6.15 6.28 6.31 6.39 3.12 3.17 3.32
2015-02-10 26.38 5.94 6.05 6.15 6.33 6.39 6.46 3.01 3.16 3.31
Output
输出
>>> vols.index
<class 'pandas.tseries.index.DatetimeIndex'>
[2015-02-12, ..., NaT]
Length: 1478, Freq: None, Timezone: None
>>> vols[date(2015,2,12)]
*** KeyError: datetime.date(2015, 2, 12)
I would expect this not to fail, and also I should be able to select a range of dates. Tried so many combinations but not getting it.
我希望这不会失败，而且我应该能够选择一个日期范围。尝试了这么多组合，但没有得到它。
采纳答案by Alex Riley
Using a datetime.dateinstance to try to retrieve the index won't work, you just need a string representation of the date, e.g. '2015-02-12'or '2015/02/14'.
使用datetime.date实例来尝试检索索引是行不通的，您只需要日期的字符串表示形式，例如'2015-02-12'或'2015/02/14'。
Secondly, vols[date(2015,2,12)]is actually looking in your DataFrame's column headings, not the index. You can use locto fetch row index labels instead. For example you could write vols.loc['2015-02-12']
其次，vols[date(2015,2,12)]实际上是查看 DataFrame 的列标题，而不是索引。您可以使用loc来获取行索引标签。例如你可以写vols.loc['2015-02-12']
