Pandas shift - how to keep the last row?-CodePudding

I've got a very simple problem. I have a dataframe:

and when I do df.shift(1) the data looks like:

     A
0  NaN
1  1.0
2  2.0

and I would like it to look like:

     A
0  NaN
1  1.0
2  2.0
3  3.0

simply speaking - how do I shift the data without losing the last row?

CodePudding user response：

Try this:

df.shift(1).append(
    df.iloc[[-1]]).reset_index(drop = True)

CodePudding user response：

just dup a nan row, then append it to the top:

import pandas as pd
import numpy as np

data = [1.0,2.0,3.0]
df = pd.DataFrame(data, columns = ['A'])
df1 = pd.DataFrame([[np.nan] * len(df.columns)], columns=df.columns)
df = df1.append(df, ignore_index=True)
print(df)  


     A
0  NaN
1  1.0
2  2.0
3  3.0