Insert header at first row, for existing csv

[mg24]

Hi Team,

I have input data in csv file like below.

1,EAST,100
2,WEST,200
3,SOUTH,300
4,NORTH,400


I want to add these headers to above input file at line one.
ID,Region,Salary


Final should look like this.

Add headers to csv
ID,Region,Salary
1,EAST,100
2,WEST,200
3,SOUTH,300
4,NORTH,400

with open("data1.csv","w") as f:
f.write()