I don't exactly know how to fix your problem, but I can point you in the right direction. In the little script below I am using openpyxl (a Python library to read/write Excel 2010 xlsx/xlsm files) to select all sheets starting with the letter 'A' and assigns them a new name.
import openpyxl
# open a new workbook
workbook_1 = openpyxl.load_workbook('file.xlsx')
# print all the existing sheetnames from workbook_1
all_sheets = workbook_1.worksheets
print(all_sheets)
# select the checker you want to use
check = 'A'
# store the selected sheets (based on the check variable) in a list
selected_sheets = [sheet for sheet in all_sheets if sheet.title[0].lower() == check.lower()]
# print the selected sheet list
print(selected_sheets)
# loop over the selected sheets
for sheet in selected_sheets:
# change the sheet title
sheet.title = 'New name'
# save the worksheet
workbook_1.save('file.xlsx')
You can find openpyxl documentation here. I think with a little effort you can solve this problem by looking at my sample script and by reading through the documentation.