Openpyxl offset: Setting cell values in rows just below a certain value

Question

I have an excel table with column names, no values, just like this:

table_name|column_a|column_b|column_c|column_d

empty row below

I have a list of values, like this [column_a, column_c]

I need a for loop that goes through the worksheet, finds a column name from the list and sets a cell value just below the column name, eg. NULL.

for row in worksheet.rows:
    for cell in row:
        if cell.value in col_names:
            cell(offset(row=1, column=0)).value='NULL' 

This is what I'm getting: NameError: name 'offset' is not defined

Edit: CharlieClark suggestion helped. Here's what I had to change

cell(offset(row=1, column=0)).value -> cell.offset(row=1, column=0).value

Answer 1

CharlieClark's suggestion helped. Here's what I had to change:

cell(offset(row=1, column=0)).value -> cell.offset(row=1, column=0).value