Question

标题说明了一切。伪代码的以下位返回以下错误：

df = pd.read_sql(query, conn, parse_dates=["datetime"],
                             index_col="datetime")
df['datetime']

我明白了：

Exception in thread Thread-1:
 Traceback (most recent call last):
   File "C:\Users\admin\.virtualenvs\EnkiForex-ey09TNOL\lib\site-packages\pandas\core\indexes\base.py", line 2656, in get_loc
     return self._engine.get_loc(key)
   File "pandas\_libs\index.pyx", line 108, in pandas._libs.index.IndexEngine.get_loc
   File "pandas\_libs\index.pyx", line 132, in pandas._libs.index.IndexEngine.get_loc
   File "pandas\_libs\hashtable_class_helper.pxi", line 1601, in pandas._libs.hashtable.PyObjectHashTable.get_item
   File "pandas\_libs\hashtable_class_helper.pxi", line 1608, in pandas._libs.hashtable.PyObjectHashTable.get_item
 KeyError: 'datetime'

我为索引datetime的行列误解了吗？我可以正常访问其他所有列。

Answer 1

索引不是列。将索引视为DataFrame的labels for the rows。 index_col='datetime'使datetime列（在csv中）成为df的索引。要访问索引，请使用df.index。

Answer 2

import pandas as pd
d = {'col1': [1, 2], 'col2': [3, 4]}
df = pd.DataFrame(d)

time = pd.date_range(end='4/5/2018',periods=2)
df.index = time
df.index

结尾是DatetimeIndex(['2018-04-04', '2018-04-05'], dtype='datetime64[ns]', freq='D') 只需使用df.index即可获取index_col的信息

熊猫index_col =“ datetime”使df ['datetime']不可用

2 个答案: