以编程方式取消保护 Excel 文件

We're getting an Excel file from a client that has open protection and Write Reserve protection turned on. I want to remove the protection so I can open the Excel file with the python xlrd module. I've installed the pywin32 package to access the Excel file through COM, and I can open it with my program supplying the two passwords, save, and close the file with no errors. I'm using Unprotect commands as described in MSDN network, and they're not failing, but they're also not removing the protection. The saved file still requires two passwords to open it after my program is done. Here's what I have so far:

import os, sys
impdir = "\\xxx.x.xx.x\allshare\IT\NewBusiness\Python_Dev\import\"
sys.path.append(impdir)
from UsefulFunctions import *
import win32com.client

wkgdir = pjoin(nbShare, 'NorthLake\_testing')
filename = getFilename(wkgdir, '*Collections*.xls*')
xcl = win32com.client.Dispatch('Excel.Application')
xcl.visible = True
pw_str = raw_input("Enter password: ")
try:
    wb = xcl.workbooks.open(filename, 0, False, None, pw_str, pw_str)
except Exception as e:
    print "Error:", str(e)
    sys.exit()
wb.Unprotect(pw_str)
wb.UnprotectSharing(pw_str)
wb.Save()
xcl.Quit()

谁能提供正确的解除保护命令的语法?