pd.ExcelWriter: export file defined in a variable to folder already created

Question

1. I create the output folder inside the directory where the script is located

dirName = './output'

os.makedirs(dirName, exist_ok=True)

2. I defined the name of the xlsx file that included the date:

from datetime import datetime

now = datetime.now()

datestr = now.strftime("%d%b%Y")

x = 'output_{}.xlsx'.format(datestr)

3. This is the tricky part, since I cannot place x inside './output'

writer = pd.ExcelWriter(x, engine='xlsxwriter')

How can I create a path that includes the folder './output' where the x object should be placed?