read multiple .xlsx files and text files in a directory

[volcano63]

#!/usr/bin/python

import os
from openpyxl.reader.excel import load_workbook
import csv

I am not sure why are you using openpyxl.reader.excel, I just checked a code I've written several week ago

from openpyxl import Workbook, load_workbook

Works just fine.  

wb.get_sheet_by_name causes exception if the sheet with that name does not exist - but I guess that is not your problem.

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PS I am not sure why, but it is recommended to open csv files with newline='' argument

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Another thing - you are collecting the same data for each Excel file you find. It is sort of inefficient. What exactly are you trying to do?