选择当前行中列值为 1 但上一行中值为 0 的行

Question

I am working with a DataFrame on Python 3.8 where I try to replicate Excel calculations - a basic if with two criteria, one of which is referencing itself a row before.

Backtest['trade_price']=0
Backtest.loc[(Backtest['z_en_crit']==1) & 
             (Backtest['trade_price'].shift(-1)==0), "trade_price"] = 1

The second criterion seems to be completely ignored... as trade_price should have only one 1

                           z_en_crit  trade_price
Datetime                                         
2020-10-21 11:00:00+01:00        0.0            0
2020-10-21 12:00:00+01:00        0.0            0
2020-10-21 13:00:00+01:00        1.0            1
2020-10-21 14:00:00+01:00        1.0            1
2020-10-21 15:00:00+01:00        1.0            1
2020-10-21 16:00:00+01:00        0.0            0

If you have any idea how to make this work and also make it faster I'd really appreciate it! Thanks!

EDIT:

Required output:

                           z_en_crit  trade_price
Datetime                                         
2020-10-21 11:00:00+01:00        0.0            0
2020-10-21 12:00:00+01:00        0.0            0
2020-10-21 13:00:00+01:00        1.0            1
2020-10-21 14:00:00+01:00        1.0            0
2020-10-21 15:00:00+01:00        1.0            0
2020-10-21 16:00:00+01:00        0.0            0

Answer 1

Are you looking to shift on "z_en_crit" instead? Also, you should reverse the direction of the shift if you want to match on the first of the group, not the last.

df['trade_price'] = np.where(
    df['z_en_crit'].eq(1) & df['z_en_crit'].shift(1).eq(0), 1, 0)

df

                           z_en_crit  trade_price
Datetime                                         
2020-10-21 11:00:00+01:00        0.0            0
2020-10-21 12:00:00+01:00        0.0            0
2020-10-21 13:00:00+01:00        1.0            1
2020-10-21 14:00:00+01:00        1.0            0
2020-10-21 15:00:00+01:00        1.0            0
2020-10-21 16:00:00+01:00        0.0            0