Use xlrd - it's faster, cross-platform, and works directly with the file.
As of version 0.8.0, xlrd reads both XLS and XLSX files.
But as of version 2.0.0, support was reduced back to only XLS.
wb = xlrd.open_workbook('your_workbook.xls')
sh = wb.sheet_by_name('Sheet1')
your_csv_file = open('your_csv_file.csv', 'wb')
wr = csv.writer(your_csv_file, quoting=csv.QUOTE_ALL)
for rownum in xrange(sh.nrows):