Python : Multiple excel files in folders and sub-folders

I have a folder with the following structure,

Folder
     |_ File1.xlsx
     |_ File1.xlsx
     ...
     |_ Folder2.xlsx
                 |_File3.xlsx
                 |_File4.xlsx

There are three aims that I want to fulfill,

  1. List out all files in folders and sub-folders.

  2. Open all files one-by-one.

  3. Copy the columns 1, 3 and 8 and store it in another excel file.

As of now, I have successfully done (1) and the code is as follows, import os

rootdir = os.getcwd()

for subdir, dirs, files in os.walk(rootdir):
    for file in files:
        filepath = subdir + os.sep + file

        if filepath.endswith(".xlsx"):
            print (filepath)

However, I am stuck at (2), I have tried to think of ways (and google) to get around it and have failed.

Any kind of help will be appreciated.

Thanks in advance.