1

在这里，我将时间添加到仅给出日期的数据中。值之间有 5 分钟或每个日期 288 个值。
该代码在输入数据帧为 1 天（288 行）或更短时有效，但在输入较长时会出错。知道我错过了什么吗？提前致谢。

相关代码部分：

import datetime as dt
print("Print df_raw:\n", df_raw)

df = df_raw[:288]
# df = df_raw[:289]  # Gives KeyError, see traceback below
print("\nPrint df BEFORE groubpy/apply:\n", df)
df.loc[:,'date'] = pd.to_datetime(df.date)

def f(x): 
    x['DT']=[val+dt.timedelta(minutes=(pos*5)) for val,pos in zip(x.loc[:,'date'], range(0,len(x.loc[:,'date'])))]
    return x

df = df.groupby('date').apply(f)
df = df.set_index('DT').drop(columns='date')

print("\nPrint df AFTER groubpy/apply:\n", df)

输出（288 行或更少，按预期工作）：

Print df_raw:
           date   values
0   2015-03-10   556.25
0   2015-03-10  516.993
0   2015-03-10   468.75
0   2015-03-10  432.812
0   2015-03-10  87.1095
..         ...      ...
84  2014-12-16     None
84  2014-12-16     None
84  2014-12-16  160.938
84  2014-12-16  145.118
84  2014-12-16  125.977

[24480 rows x 2 columns]

Print df BEFORE groubpy/apply:
           date   values
0   2015-03-10   556.25
0   2015-03-10  516.993
0   2015-03-10   468.75
0   2015-03-10  432.812
0   2015-03-10  87.1095
..         ...      ...
0   2015-03-10  781.446
0   2015-03-10   743.36
0   2015-03-10  708.985
0   2015-03-10  669.922
0   2015-03-10  632.422

[288 rows x 2 columns]

Print df AFTER groubpy/apply:
                       values
DT                          
2015-03-10 00:00:00   556.25
2015-03-10 00:05:00  516.993
2015-03-10 00:10:00   468.75
2015-03-10 00:15:00  432.812
2015-03-10 00:20:00  87.1095
...                      ...
2015-03-10 23:35:00  781.446
2015-03-10 23:40:00   743.36
2015-03-10 23:45:00  708.985
2015-03-10 23:50:00  669.922
2015-03-10 23:55:00  632.422

[288 rows x 1 columns]

回溯（有 289 行或更多，我明白了）：

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\groupby\groupby.py in apply(self, func, *args, **kwargs)
    724             try:
--> 725                 result = self._python_apply_general(f)
    726             except Exception:

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\groupby\groupby.py in _python_apply_general(self, f)
    744         return self._wrap_applied_output(
--> 745             keys, values, not_indexed_same=mutated or self.mutated
    746         )

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\groupby\generic.py in _wrap_applied_output(self, keys, values, not_indexed_same)
    371         elif isinstance(v, DataFrame):
--> 372             return self._concat_objects(keys, values, not_indexed_same=not_indexed_same)
    373         elif self.grouper.groupings is not None:

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\groupby\groupby.py in _concat_objects(self, keys, values, not_indexed_same)
    954                 else:
--> 955                     result = result.reindex(ax, axis=self.axis)
    956 

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\util\_decorators.py in wrapper(*args, **kwargs)
    220         def wrapper(*args, **kwargs):
--> 221             return func(*args, **kwargs)
    222 

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\frame.py in reindex(self, *args, **kwargs)
   3975         kwargs.pop("labels", None)
-> 3976         return super().reindex(**kwargs)
   3977 

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\generic.py in reindex(self, *args, **kwargs)
   4513         return self._reindex_axes(
-> 4514             axes, level, limit, tolerance, method, fill_value, copy
   4515         ).__finalize__(self)

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\frame.py in _reindex_axes(self, axes, level, limit, tolerance, method, fill_value, copy)
   3863             frame = frame._reindex_index(
-> 3864                 index, method, copy, level, fill_value, limit, tolerance
   3865             )

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\frame.py in _reindex_index(self, new_index, method, copy, level, fill_value, limit, tolerance)
   3885             fill_value=fill_value,
-> 3886             allow_dups=False,
   3887         )

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\generic.py in _reindex_with_indexers(self, reindexers, fill_value, copy, allow_dups)
   4576                 allow_dups=allow_dups,
-> 4577                 copy=copy,
   4578             )

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\internals\managers.py in reindex_indexer(self, new_axis, indexer, axis, fill_value, allow_dups, copy)
   1250         if not allow_dups:
-> 1251             self.axes[axis]._can_reindex(indexer)
   1252 

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\indexes\base.py in _can_reindex(self, indexer)
   3361         if not self.is_unique and len(indexer):
-> 3362             raise ValueError("cannot reindex from a duplicate axis")
   3363 

ValueError: cannot reindex from a duplicate axis

During handling of the above exception, another exception occurred:

KeyError                                  Traceback (most recent call last)
~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\indexes\base.py in get_loc(self, key, method, tolerance)
   2896             try:
-> 2897                 return self._engine.get_loc(key)
   2898             except KeyError:

pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_loc()

pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_loc()

pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.PyObjectHashTable.get_item()

pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.PyObjectHashTable.get_item()

KeyError: 'date'

During handling of the above exception, another exception occurred:

KeyError                                  Traceback (most recent call last)
<ipython-input-207-872197908aef> in <module>
     36     return x
     37 
---> 38 df = df.groupby('date').apply(f)
     39 df = df.set_index('DT').drop(columns='date')
     40 

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\groupby\groupby.py in apply(self, func, *args, **kwargs)
    735 
    736                 with _group_selection_context(self):
--> 737                     return self._python_apply_general(f)
    738 
    739         return result

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\groupby\groupby.py in _python_apply_general(self, f)
    740 
    741     def _python_apply_general(self, f):
--> 742         keys, values, mutated = self.grouper.apply(f, self._selected_obj, self.axis)
    743 
    744         return self._wrap_applied_output(

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\groupby\ops.py in apply(self, f, data, axis)
    235             # group might be modified
    236             group_axes = _get_axes(group)
--> 237             res = f(group)
    238             if not _is_indexed_like(res, group_axes):
    239                 mutated = True

<ipython-input-207-872197908aef> in f(x)
     33 
     34 def f(x):
---> 35     x['DT']=[val+dt.timedelta(minutes=(pos*5)) for val,pos in zip(x.loc[:,'date'], range(0,len(x.loc[:,'date'])))]
     36     return x
     37 

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\indexing.py in __getitem__(self, key)
   1416                 except (KeyError, IndexError, AttributeError):
   1417                     pass
-> 1418             return self._getitem_tuple(key)
   1419         else:
   1420             # we by definition only have the 0th axis

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\indexing.py in _getitem_tuple(self, tup)
    803     def _getitem_tuple(self, tup):
    804         try:
--> 805             return self._getitem_lowerdim(tup)
    806         except IndexingError:
    807             pass

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\indexing.py in _getitem_lowerdim(self, tup)
    927         for i, key in enumerate(tup):
    928             if is_label_like(key) or isinstance(key, tuple):
--> 929                 section = self._getitem_axis(key, axis=i)
    930 
    931                 # we have yielded a scalar ?

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\indexing.py in _getitem_axis(self, key, axis)
   1848         # fall thru to straight lookup
   1849         self._validate_key(key, axis)
-> 1850         return self._get_label(key, axis=axis)
   1851 
   1852 

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\indexing.py in _get_label(self, label, axis)
    158             raise IndexingError("no slices here, handle elsewhere")
    159 
--> 160         return self.obj._xs(label, axis=axis)
    161 
    162     def _get_loc(self, key: int, axis: int):

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\generic.py in xs(self, key, axis, level, drop_level)
   3727 
   3728         if axis == 1:
-> 3729             return self[key]
   3730 
   3731         self._consolidate_inplace()

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\frame.py in __getitem__(self, key)
   2993             if self.columns.nlevels > 1:
   2994                 return self._getitem_multilevel(key)
-> 2995             indexer = self.columns.get_loc(key)
   2996             if is_integer(indexer):
   2997                 indexer = [indexer]

~\AppData\Local\Continuum\miniconda3\lib\site-packages\pandas\core\indexes\base.py in get_loc(self, key, method, tolerance)
   2897                 return self._engine.get_loc(key)
   2898             except KeyError:
-> 2899                 return self._engine.get_loc(self._maybe_cast_indexer(key))
   2900         indexer = self.get_indexer([key], method=method, tolerance=tolerance)
   2901         if indexer.ndim > 1 or indexer.size > 1:

pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_loc()

pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_loc()

pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.PyObjectHashTable.get_item()

pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.PyObjectHashTable.get_item()

KeyError: 'date'

编辑
感谢所有帮助。根据您的建议，此解决方案似乎对我有用，没有SettingWithCopyWarning：

import pandas as pd
import datetime as dt

# Note: df_raw is set elsewhere...
df = df_raw

df.loc[:,'date'] = pd.to_datetime(df['date'])

em = pd.DataFrame()

for key,t in df.groupby('date'):
    temp = t
    temp.loc[:,'DT'] = [i+dt.timedelta(minutes=j*5) for i,j in zip(t['date'],range(t['date'].shape[0]))]
    em = pd.concat([em,temp])

print(em)

Python：3.7.4
熊猫：0.25.3
Jupyter Lab

4

2 回答 2

2

当您将 apply 函数与 groupby 一起使用时，您无法访问函数内部的 group 键。

相反，您可以逐组遍历分组的数据帧，并将处理后的数据帧附加在一起。

import pandas as pd

t = pd.DataFrame({'date':['2015-03-10','2015-03-10','2015-03-10','2015-03-10','2015-03-11','2015-03-11','2015-03-11'],'value':[1,2,3,4,5,6,7]})

t['date'] = pd.to_datetime(t['date'])

创建一个新的数据框并将已处理的组附加到它。

em = pd.DataFrame()

for key,df in t.groupby('date'):
    temp = df
    temp['dt'] = [i+datetime.timedelta(minutes=j*5) for i,j in zip(df['date'],range(df['date'].shape[0]))]
    em = pd.concat([em,temp])

输出：

        date  value                  dt
0 2015-03-10      1 2015-03-10 00:00:00
1 2015-03-10      2 2015-03-10 00:05:00
2 2015-03-10      3 2015-03-10 00:10:00
3 2015-03-10      4 2015-03-10 00:15:00
4 2015-03-11      5 2015-03-11 00:00:00
5 2015-03-11      6 2015-03-11 00:05:00
6 2015-03-11      7 2015-03-11 00:10:00
于 2020-02-12T20:27:47.483 回答
1

你得到了，因为当你在 groupby 之后KeyError: 'date'使用它时，它没有被传递到函数中。apply()例如，您尝试将 lambda 添加到应用中。我不确定预期的行为，但它使功能正常工作。将其更改为：

df = df.groupby('date').apply(lambda x: f(x))

完整的工作示例：

import datetime as dt
df = pd.DataFrame({'A':[1,2],'date':['2018-09-09','2019-09-09']})
df.loc[:,'date'] = pd.to_datetime(df['date'])
def f(x): 
    x['DT']=[val+dt.timedelta(minutes=(pos*5)) for val,pos in zip(x.loc[:,'date'], range(0,len(x.loc[:,'date'])))]
    return x

df = df.groupby('date').apply(lambda x : f(x))
df = df.set_index('DT').drop(columns='date')
print(df)

输出：

            A
DT           
2018-09-09  1
2019-09-09  2
于 2020-02-12T20:03:39.143 回答