Pandas(Python) : How to fill empty cells with previous row value with conditions

Question

For order dataset where Customer name ( Name ) per order are not repeated and some order does not have customer name. Example:

How can I make the name is repeated like:

I wonder if it's still possible to use ffill() with condition that order id should be the same

Answer 1

Try:

df=pd.DataFrame({'order id':['A1','A1','A2','A3'],'Name':['Adam',np.nan,np.nan,'su']})
df['Name']=df['Name'].groupby(df['order id']).fillna(method='ffill')

df
Out[28]: 
  order id  Name
0       A1  Adam
1       A1  Adam
2       A2   NaN
3       A3    su

Answer 2

You have to use groupby and then fill. If you want to apply the fill operation only on the "Name" column, it should look like this:

import pandas as pd
import numpy as np
data = {"order_id": [1,1,2,3], "name":["adam", np.nan, np.nan, "Su"],"total":            [15,np.nan, 5, 10]}
df = pd.DataFrame(data)
df["name"] = df.groupby("order_id")["name"].fillna(method='ffill')

Answer 3

You can use this

DataFrame.fillna(method="ffill", axis=1, limit=1)