Вы можете append
один кадр в другой и использовать интерполировать () , пример:
df1 = pd.DataFrame(columns=['ds', '1_sensor_id', '1_val_1', '1_val_2'],
data=[[datetime.datetime(2019, 9, 13, 12, 40, 00), 33469, 30, 43],
[datetime.datetime(2019, 9, 13, 12, 45, 00), 33469, 33, 43]])
df2 = pd.DataFrame(columns=['ds', '2_sensor_id', '2_val_1', '2_val_2'],
data=[[datetime.datetime(2019, 9, 13, 12, 42, 00), 20006, 6, 50],
[datetime.datetime(2019, 9, 13, 12, 47, 00), 20006, 5, 80]])
df = df1.append(df2, sort=False)
df.set_index('ds', inplace=True)
df.interpolate(method = 'time', limit_direction='backward', inplace=True)
print(df)
1_sensor_id 1_val_1 ... 2_val_1 2_val_2
ds ...
2019-09-13 12:40:00 33469.0 30.0 ... 6.0 50.0
2019-09-13 12:45:00 33469.0 33.0 ... 5.4 68.0
2019-09-13 12:42:00 NaN NaN ... 6.0 50.0
2019-09-13 12:47:00 NaN NaN ... 5.0 80.0