Fill down between rows in new dataframe column

Question

I have a dataframe where I need to create a new column (Break), and forward fill that column between all the Break rows.

Type,Name
Parent,Parent1
Break,break010
Op,Op1
Unit,Unit1
Item,Item1
Break,break020
Op,Op2
Unit,Unit2
Break,break030
Op,Op3
Unit,Unit3
Parent,Parent2
Break,break010

For example, the output should be

  Type       Name      Break
Parent    Parent1   
 Break   break010   break010
    Op        Op1   break010
  Unit      Unit1   break010
  Item      Item1   break010
 Break   break020   break020
    Op        Op2   break020
  Unit      Unit2   break020
 Break   break030   break030
    Op        Op3   break030
  Unit      Unit3   break030
Parent    Parent2   
 Break   break010   break010

Asked By: user53526356

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Source

Answer 1

You can use DataFrame.where() to replace values that are not "Break":

df["Break"] = df["Name"].where(df.Type == "Break", pd.NA).ffill().where(df.Type != "Parent", "")

This takes the "Name" column, and returns pd.NA where the "Type" column is not "Break", then forward fills the values, and finally sets all columns where "Type" is "Parent" to "".

Answered By: Rawson

Fill down between rows in new dataframe column

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