class SheetsList:
    def __init__(self, master, title, row, column):
        self.var = tk.BooleanVar()
        self.var.set(0)
        self.title = title
        self.row = row
        self.column = column
        self.cb = tk.Checkbutton(master, text=title, variable=self.var, onvalue=1, offvalue=0, bg="cyan3", )
        self.cb.grid(row=row, column=column, rowspan=2, padx=5, pady=5, sticky="nw")
def file_check():
    global wb, sheet_names, quantity_sheets, checks, sheet
    print(filename)
    wb = load_workbook(filename)
    quantity_sheets = len(wb.sheetnames)
    sheet_names = [wb.sheetnames]
    checks = []
    c = 0
    r = -1
    for i in range(0, quantity_sheets):
        sheet[i] = wb.sheetnames[i]
        if r < 4:
            r += 1
        else:
            r = 0
            c += 1
        checks.append(SheetsList(app.frame2, sheet[i], r, c))