Pandas assign a pd series with longer len than df, to a col in that df

import pandas as pd
df = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]})
new_series = pd.Series([7, 8,9,10], name='C')
df['B'] = new_series

in this code the column ‘B’ does not get replaced with new series. so I want the df to be

df["B"]=[1, 2, 3,nan]
df["B"]=[7, 8,9,10]

>Solution :

Make indices between df and new_series agreed, then – assign the needed column:

df.reindex(new_series.index).assign(B=new_series)

     A   B
0  1.0   7
1  2.0   8
2  3.0   9
3  NaN  10