Excel formatting in python without loading workbook

Question

I am trying to format an excel document within python that I am creating in the same script. All of the answers I have found have involved loading an existing workbook into python and formatting from there. In my script, I am currently writing the entire unformatted excel sheet, saving the file, then immediately reloading the document in to python to format. This is the only workaround I can find so that I can have an active sheet.

writer=pd.ExcelWriter(file_name, engine='openpyxl')
writer.save()#saving my file
wb=load_workbook(file_name) #reloading file to format
ws=wb.active
ws.column_dimensions['A'].width=33
ws.column_dimensions['B'].width=16 
wb.save(file_name)

This works to change aspects such as column width, but I would like a way to format the page without saving and reloading. Is there a way to get around the need for an active sheet when there is no file_name written yet? I want a way to remove line 2 and 3, however that may be.

Answer 1

The object that Pandas is creating in ExcelWriter depends on the "engine" you give it. In this case, you're passing along "openpyxl", so ExcelWriter is making an openpyxl.Workbook() object. You can create a new Workbook in openpyxl using "Workbook()" Like so:

https://openpyxl.readthedocs.io/en/default/tutorial.html#create-a-workbook

It is created with 1 active sheet. Basically:

import openpyxl

wb = openpyxl.Workbook()
ws=wb.active
ws.column_dimensions['A'].width=33
ws.column_dimensions['B'].width=16 
wb.save(file_name)

...would do the job

Answer 2

Your title is misleading: you're working in Pandas and dumping to Excel. Pandas does allow some formatting for this but, because it tries to support different Python libraries (openpyxl, xlsxwriter and xlwt) there are restrictions on this.

For full control openpyxl provides support for Pandas' DataFrame objects: http://openpyxl.readthedocs.io/en/latest/pandas.html