I have this exact problem: https://www.en.adwords-community.com/t5/Basics-for-New-Advertisers/Character-Encoding-used-by-the-editor/td-p/100244
which can apparently be solved by writing a byte order mark first to the file. But how do I do this with xlwt? Can I just write it to the first cell of the first worksheet? Or do I need to like write the file and then append it to a new file that's just a byte order mark? I can't find any resources on this.