After many hours of research finally, I found it. This code decides the best fit for the columns. I feel this answers you question because you are using the word Auto-fit
NOTE : In the below code, sheet is the worksheet name. Usually in the documentation, we can see it as ws. Please don't forget to change the worksheet name.
# Imorting the necessary modules
try:
from openpyxl.cell import get_column_letter
except ImportError:
from openpyxl.utils import get_column_letter
from openpyxl.utils import column_index_from_string
from openpyxl import load_workbook
import openpyxl
from openpyxl import Workbook
for column_cells in sheet.columns:
new_column_length = max(len(str(cell.value)) for cell in column_cells)
new_column_letter = (get_column_letter(column_cells[0].column))
if new_column_length > 0:
sheet.column_dimensions[new_column_letter].width = new_column_length*1.23
UPDATE : This code doesn't work for all, but don't hesitate to try it