In [7]:
import numpy as np
import pandas as pd

from datetime import date

In [16]:
df = pd.DataFrame({
    'date': pd.to_datetime([date(2019,1,d) for d in range(1,11)]),
    'reading': np.random.uniform(high=100,size=10)
})

In [17]:
df


Out[17]:
date reading
0 2019-01-01 98.884397
1 2019-01-02 50.127106
2 2019-01-03 18.173642
3 2019-01-04 55.048161
4 2019-01-05 76.951160
5 2019-01-06 53.121246
6 2019-01-07 4.793864
7 2019-01-08 12.145948
8 2019-01-09 89.761799
9 2019-01-10 83.014272

In [22]:
df['reading_d_minus_1']= df['reading'].shift(1)

In [23]:
df


Out[23]:
date reading reading_d_minus_1
0 2019-01-01 98.884397 NaN
1 2019-01-02 50.127106 98.884397
2 2019-01-03 18.173642 50.127106
3 2019-01-04 55.048161 18.173642
4 2019-01-05 76.951160 55.048161
5 2019-01-06 53.121246 76.951160
6 2019-01-07 4.793864 53.121246
7 2019-01-08 12.145948 4.793864
8 2019-01-09 89.761799 12.145948
9 2019-01-10 83.014272 89.761799