Comment 4 for bug 1687013

book = xlrd.open_workbook('Excel.sikuli/myfile.xls')
worksheet = workbook.sheet_by_name('Sheet 1')

since you named your xls-object
book = xlrd.open_workbook('Excel.sikuli/myfile.xls')

you have to use
worksheet = book.sheet_by_name('Sheet 1')

Sorry, but this is either basic Python knowledge or can be solved by consulting the docs of an offending module.