如何将数据帧的一列的值复制到熊猫中其他数据帧的另一列？

Question

在将字符串列的值一一复制到另一个数据框的列时，我将其作为包含方括号的输出：

chk.at[index,'StartLocation1'] = chkn['StartLocation1'].values
chk.at[index,'EndLocation1'] = chkn['EndLocation1'].values

0        [Petrol Pump-Ramji Ambedkar Nagar]
1                           [V Enterprises]
2                                   [Baola]
3                         [Dharmajyot-Vapi]
4    [KINGSTON TOWER VASAI Dominos-(THANE)]
Name: StartLocation1, dtype: object

所以我想删除这个 [] 括号：我已经应用了这个：

chk['EndLocation1'].str.strip('[]').astype(str)

0      nan
1      nan
2      nan
3      nan
4      nan

但是，我有 nan 值。 请支持！

看到这是我的全部代码：

chk['StartLocation1'] = ''
chk['EndLocation1'] = ''

for index, row in chk.iterrows():
    start = row.StartTime
    end = row.EndTime
    reg = row.RegistrationNo

    query = "SELECT TOP 1 RegistrationNo, GPSDateTime, Location  FROM GPSEventsDataCurrentWeek where GPSDateTime Between 'start_date' and 'end_date' and RegistrationNo = 'reg' and GroundSpeed > 0 ORDER BY GPSDateTime ASC"

    query = query.replace('start_date', start.strftime('%m/%d/%Y %H:%M:%S'))
    query = query.replace('end_date', end.strftime('%m/%d/%Y %H:%M:%S'))
    query = query.replace('reg', str(reg))

    chk1 = pd.read_sql(query, con=engine)
    

    chk1 = chk1.rename({'Location': 'StartLocation1','GPSDateTime': 'StartTime'}, axis=1)
   

    query2 = "SELECT TOP 1 RegistrationNo, GPSDateTime, Location  FROM GPSEventsDataCurrentWeek where GPSDateTime Between 'start_date' and 'end_date' and RegistrationNo = 'reg' and GroundSpeed > 0 ORDER BY GPSDateTime DESC"

    query2 = query2.replace('start_date', start.strftime('%m/%d/%Y %H:%M:%S'))
    query2 = query2.replace('end_date', end.strftime('%m/%d/%Y %H:%M:%S'))
    query2 = query2.replace('reg', str(reg))

    chk2 = pd.read_sql(query2, con=engine)
    

    chk2 = chk2.rename({'Location': 'EndLocation1','GPSDateTime': 'EndTime'}, axis=1)
  
    chkn = pd.merge(chk1,chk2, on = ['RegistrationNo'], how = 'outer')
    print(chkn[['StartLocation1','EndLocation1']])
    

    chk.at['StartLocation1'] = chkn['StartLocation1'].values
    chk.at[index,'EndLocation1'] = chkn['EndLocation1'].values

这是我的数据框 chk：

Companyid   RegistrationNo  Date    Hour    Value   RunningDuration StartTime   EndTime
0   236.0   MH-01-CJ-3571   2020-09-01  0.0 True    00:42:00    2020-09-01 00:08:00 2020-09-01 00:59:00
1   236.0   MH-01-CV-7460   2020-09-01  0.0 True    00:49:00    2020-09-01 00:09:00 2020-09-01 00:58:00
2   654.0   MH-04-JK-4102   2020-09-01  0.0 True    00:03:00    2020-09-01 00:11:00 2020-09-01 00:24:00
3   654.0   DN-09-R-9421    2020-09-01  0.0 True    00:02:00    2020-09-01 00:24:00 2020-09-01 00:54:00
4   236.0   MH-01-CV-7456   2020-09-01  0.0 True    00:04:00    2020-09-01 00:38:00 2020-09-01 00:42:00

Answer 1

也许一个可能的解决方案是通过列表元素的连接选择列表中的唯一值（ python 中的列表连接列表）。 df.values 返回一个 n 数组对象，因此返回的值是一个长度为 1 的列表，但建议使用 df.to_numpy 代替（ https://pandas.pydata.org/pandas-docs/stable/reference/api/ pandas.DataFrame.values.html )

无论如何，我认为以这种方式分配列并不是最好的方法。