In my first semester of Ph.D., I took a course about machine learning (ML), because I find it very fancy and interesting (however, my field of research is theoretical physics, far away from ML).

The professor who taught ML was an old and super cool guy. He made this course a real fun to learn. Now after one year, as a side project, I wrote a "deepfake" ML algorithm (of course, it had already been done, and I took a lot of help from GitHub), but still, the content that I learned in my ML course was very helpful in all this process.

I was about to write an email to the professor who taught the ML course. I wonder if it is okay to send something like, "Professor, I am really very thankful to you for putting all the effort into making the ML course easy and fun. Here is what I have achieved from the content that you taught me [attachments]"?

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    This looks completely OK to me. Oct 30, 2020 at 22:24
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    I cannot imagine any gifted teacher that is not pleased to see his students making good use of the skills acquired in their course. Oct 31, 2020 at 1:57
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    I recently sent an a thank-you email to a professor who taught a course I took in my second last year of undergrad, which was well over 5 years ago, since then i had done a PhD and then gone into industry, where his teachings were suddenly very relevent. He (i suspect vaguely) remembered who i was and was please to hear what i had been up to and how useful the things he taught me were. He seemed happy to get the email. Nov 1, 2020 at 21:47
  • Deepfakes is potentially a bit of a controversial subject due to the ethical concerns. I would be at least a little hesitant to mention working on that to someone, even on the assumption that you're neither doing anything questionable with it nor furthering research on the topic.
    – NotThatGuy
    Nov 2, 2020 at 12:51
  • I put in practice something that an instructor taught me about two years prior, and I was sure that my success at implementing it was directly due to that instructor's influence, so I wrote an email to her. She always gave curt 1 or 2 line responses to emails or our class message board when I was her student, but she responded to me with a three paragraph message talking about how excited she gets when her students are able to use their skills in the real world. Not every teacher may be that excited, but I can't imagine anyone not being happy to hear about how they assisted your success.
    – Davy M
    Nov 2, 2020 at 21:17

3 Answers 3


Yes, it is entirely appropriate and will be appreciated. Let the person know a bit about your current activities - especially successes.

Even better, if it weren't for the pandemic, would be to pay them an in-person visit during office hours. Too few people get a chance to thank their important mentors, I'm afraid.

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    I'm surprised you're suggesting to drop in. I would expect that at least some teachers don't want to take the time to chat a bit when they have other things that need to be done. (I'm a student, to clarify my perspective)
    – lucidbrot
    Nov 1, 2020 at 12:09
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    @lucidbrot Everyone takes breaks. There is probably a coffee room somewhere, also. By "office hours" I intended the time set aside to see students. Most places require a few hours a week.
    – Buffy
    Nov 1, 2020 at 12:14
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    @lucidbrot As long as you're mindful of social signals (don't barge in if the door is closed, don't stay talking while they keep looking at their watch) most professors are happy to see past students. Especially the type who spent the time to make their course cool and interesting, and especially if you are coming to tell them nice things about how you enjoyed their course. Nov 2, 2020 at 15:33
  • I also would think office hours are no good idea. The professor may be a bit nervous about having reserved the time for student questions and maybe needing to stop chatting with you when a student comes to ask something. If you did something cool, maybe you could arrange a separate appointment where both of you now you have time without interruptions from people who have a legitimate interest to interrupt you.
    – allo
    Nov 2, 2020 at 23:39

Yes it is entirely appropriate. Good unsolicited comments from students are always useful when one has to fill out annual reports or other such paperwork.

You might care to also include their immediate superiors (Chair or Dean) in the list of recipients to maximize the impact of your email.

  • 21
    I'm appalled by the mere utilitarian tone of this answer, limiting the impact of such a thank you email to the annual paperwork. Along 20 years of teaching, I've received many thank you emails or speeches from students: I'm pretty sure they wouldn't have been written or said the way they did, if the students had to share them with my higher ups. For annual reporting and higher-ups, there are the teaching evaluations: keep personal communications personal. Oct 31, 2020 at 2:45
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    @MassimoOrtolano interesting but I strongly disagree. There can be no doubt that one relishes compliments but telling an instructor in an email he or she was great makes 0 impact to anyone but the instructor. If a student was much influenced through mentoring of an instructor, then much better IMO to tell the higher-ups so this is recognized properly. If you still have faith in course evaluation then I’m afraid that my local world is different from yours. Oct 31, 2020 at 4:20
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    @ZeroTheHero: makes 0 impact to anyone but the instructor. Sometimes that's specifically what the former student was aiming for - a human social interaction, nothing more. A generally good teacher doesn't need to scraper together random emails to keep their department happy with their teaching, do they? Oct 31, 2020 at 13:21
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    @PeterCordes I happen to think that the types of mentor described by the OP should be celebrated. Inspirational and aspirational instructors are too few and far between. Oct 31, 2020 at 14:15
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    I think for most 'normal' students, thinking about promoting an instructor to their chair or dean is not even remotely on their radar. As a result I feel like this would come across as being somewhat disingenuous. Perhaps a separate email to the chair/dean is ok, but again almost no students I know of are going to be thinking along those lines.
    – Cole
    Nov 2, 2020 at 5:02

I think that a general thank-you email is absolutely okay. Moreover, I think the professor will most probably be really glad to hear a thank you not from fresh graduates who simply liked the course, but from a person who obviously found the course really useful and applicable for whatever they are doing. You may want to include what you have done, why you worked on it, show some results, etc.

Also, a good idea will be to link it all to the course (e.g. "I found this and that topics really useful", or "I followed books A and B that you recommended, the former seemed too formal to me, but the latter was very useful", or "You did not mention Foobar transform, but this was what made everything very easy"). After all, this is probably the information that the professor really wants to hear, as such a feedback will allow them to do any adjustments to their course.

However, I would suggest you not to include specific details such as a GitHub link or source code attached. I'm not a professor, but I teach programming and algorithms to high school students, and I always find it a bit awkward when my former students send me some of their new code. What do they expect me to do with it? Do they want me to review the code, give some suggestions, etc.? If yes, then most often I would not be able to do such a review, yet alone just read the code. If not, then why include the code?

Of course, I can skim the code and just reply something like "Thanks, this looks great", but this seems to be not correct, because I did not really study the code and can not say that it is great. Moreover, in my course I'm rather strict about code quality, and so saying that some code is "great" without thoroughly reviewing it is below my standards...

What I am really glad to know is that the students have found my course useful in real life. I'll be glad to know what specific parts of the course were especially useful. I'll be glad to know what are they working on, and even discuss any specific questions they may have. But sending a large code without a specific request puts me in an awkward position. Think of it as of posting that huge code to Stack Overflow...

So don't include the code or any other information that may require a great deal of attention from the professor. If the professor will be interested, they would ask for the details they want.

This may be cultural, of course.

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