How to replace columns based on another column (matching parent id with id) python

Question

I have a dataset that looks like this

ID	TITLE	PARENT_ID
1	Tom	NaN
2	Lisa	1
3	Lecy	1
4	Ann	NaN
5	John	NaN
6	Lana	4

If Lisa's PARENT_ID is 1, then her parent is Tom. If tom has NaN parent_id, means he is not child, he is parent. So that, I need it to look like this:

ID	TITLE	PARENT_ID
1	Tom	NaN
2	Lisa	Tom
3	Lecy	Tom
4	Ann	NaN
5	John	NaN
6	Lana	Ann

Answer 1

you can use map

df['PARENT_ID_FINAL']=df['ID'].map(dict(zip(df['ID'],df['TITLE'])))