python 3.x – Script does not apply changes to xlsx

I write because I am developing a script to screen repeated records in an excel with openpyxl. The script is as follows:

import openpyxl as xl

def main (file):
    wb = xl.load_workbook (file)
    sh = wb.active
    store = []
    for and in range (1, 1 + sh.max_row):
        store.append (sh["B" + str(e)].value)

    many = []
    for and in store:
        if many.count (e) <1 < store.count(e):
            many.append(e)

    for e in range(1, 1 + sh.max_row):
        count = 0
        if many.count(sh["B" + str(e)].value) > 0 and count> 0:
            sh["J" + str(e)].value = "N"
        elif many.count (sh["B" + str(e)].value)> 0:
            count + = 1

    wb.save (file.replace (".xlsx", "_act.xlsx"))

What it does is: take all the possible values ​​in column B, see which ones are repeated (that is, they are present more than once) and separate them (it does so in a separate list, hence the A <1 <B , since I want the count of the same in the separate list to be less than 1 and that the count in the list of records be greater than 1). Once you have the separate list, look at record to record in column B if it is present in the repeated list. If it is and is not the first instance of it, mark it in column J with an "N" to be able to separate it via excel later.

The fact is that, as I execute it, it returns a copy of the original (and I know it is a copy because I know that there are repeated records in column B.

Thanks in advance