两个日期之间的月份 - pandas 系列和 datetime.date.today()

Question

我正在尝试计算两个日期之间的月数。我正在 pandas 系列上运行该操作。

示例系列：

3645   2014-06-24
3646   2020-11-03
3647   2016-06-28
3648   2017-07-20
3649   2000-03-27
Name: lastSaleDate, Length: 1797, dtype: datetime64[ns]

我想计算自该日期以来的月数，即列中的日期与今天之间的差异。

import pandas as pd
import datetime as dt
import numpy as np

# Calc. months since last txn
df['mos'] = ((df.Date - dt.date.today())/np.timedelta64(1, 'M'))

回溯：

TypeError                                 Traceback (most recent call last)
/var/folders/d0/gnksqzwn2fn46fjgrkp6045c0000gn/T/ipykernel_92607/847000123.py in <module>
      5 
      6 # Calc. months 
----> 7 df['mos'] = ((df.Date - dt.date.today())/np.timedelta64(1, 'M'))

/Applications/Anaconda/anaconda3/lib/python3.9/site-packages/pandas/core/ops/common.py in new_method(self, other)
     67         other = item_from_zerodim(other)
     68 
---> 69         return method(self, other)
     70 
     71     return new_method

/Applications/Anaconda/anaconda3/lib/python3.9/site-packages/pandas/core/arraylike.py in __sub__(self, other)
     98     @unpack_zerodim_and_defer("__sub__")
     99     def __sub__(self, other):
--> 100         return self._arith_method(other, operator.sub)
    101 
    102     @unpack_zerodim_and_defer("__rsub__")

/Applications/Anaconda/anaconda3/lib/python3.9/site-packages/pandas/core/series.py in _arith_method(self, other, op)
   5524 
   5525         with np.errstate(all="ignore"):
-> 5526             result = ops.arithmetic_op(lvalues, rvalues, op)
   5527 
   5528         return self._construct_result(result, name=res_name)

/Applications/Anaconda/anaconda3/lib/python3.9/site-packages/pandas/core/ops/array_ops.py in arithmetic_op(left, right, op)
    216         # Timedelta/Timestamp and other custom scalars are included in the check
    217         # because numexpr will fail on it, see GH#31457
--> 218         res_values = op(left, right)
    219     else:
    220         # TODO we should handle EAs consistently and move this check before the if/else

TypeError: unsupported operand type(s) for -: 'DatetimeArray' and 'datetime.date'

Answer 1

正如错误所示，类型不匹配。您必须将 datetime.date 对象转换为 pandas datetime，或者可以使用 to_datetime('today') 代替：

df['mos'] = df['lastSaleDate'].rsub(pd.to_datetime('today'))/np.timedelta64(1, 'M')

或（更易读）

df['mos'] = (pd.to_datetime('today') - df['lastSaleDate'])/np.timedelta64(1, 'M')

输出：

3645     92.710100
3646     16.355349
3647     68.561760
3648     55.846920
3649    263.621207
Name: dates, dtype: float64