Question

我想在新定义的“日期”列中组合年，月和日。我使用this link来实现自己的目标。我名为z的数据框具有如下数据框：

   Year  Month  day  Hour  Minute  Second   Latitude  Longirude  Exact  
0  1992     12   31    23      59      59  29.456137  85.506958      0   
1  2017     10    1     4      35      38  27.694225  85.291702      0   
2  2017     10    1     6      13      18  28.962729  80.912323      0   
3  2017     10    2     5      18      31  27.699097  85.299431      0   
4  2017     10    3     4      23      20  27.700438  85.329933      0

我的代码如下：

z['Date'] = z.apply(lambda row: datetime(int(row['Year']), int(row['Month']), int(row['day']), axis=1))

但是，它给了我错误：

Traceback (most recent call last):

  File "<ipython-input-40-3d0f2cb862d4>", line 1, in <module>
    z['Date'] = z.apply(lambda row: datetime(int(row['Year']), int(row['Month']), int(row['day']), axis=1))

  File "/usr/lib/python3/dist-packages/pandas/core/frame.py", line 3972, in apply
    return self._apply_standard(f, axis, reduce=reduce)

  File "/usr/lib/python3/dist-packages/pandas/core/frame.py", line 4064, in _apply_standard
    results[i] = func(v)

  File "<ipython-input-40-3d0f2cb862d4>", line 1, in <lambda>
    z['Date'] = z.apply(lambda row: datetime(int(row['Year']), int(row['Month']), int(row['day']), axis=1))

  File "/usr/lib/python3/dist-packages/pandas/core/series.py", line 557, in __getitem__
    result = self.index.get_value(self, key)

  File "/usr/lib/python3/dist-packages/pandas/core/index.py", line 1790, in get_value
    return self._engine.get_value(s, k)

  File "pandas/index.pyx", line 103, in pandas.index.IndexEngine.get_value (pandas/index.c:3204)

  File "pandas/index.pyx", line 111, in pandas.index.IndexEngine.get_value (pandas/index.c:2903)

  File "pandas/index.pyx", line 159, in pandas.index.IndexEngine.get_loc (pandas/index.c:3908)

KeyError: ('Year', 'occurred at index Year')

我还通过enter link description here检查了这是什么错误。但是我没有发现任何遗漏的列或空白错误。

Answer 1

最好使用pd.to_datetime：

z['Date'] = pd.to_datetime(df[['Year','Month','day']])

>>> z['Date']
0   1992-12-31
1   2017-10-01
2   2017-10-01
3   2017-10-02
4   2017-10-03
Name: Date, dtype: datetime64[ns]

通过这种方式，您可以获得易于与pandas date functionality

一起使用的日期时间序列。

但是，通过一些调整，您的方法仍然有效， ie 将axis参数移到对apply的调用中，而不是对{{1}的调用中}：

datetime

KeyError ：（“年份”，“发生在索引年份”）

1 个答案: