Append users' input to global dataframe

I have the following use case in mind:
I want to show different images to different users (randomly) and have them annotate what they see, e.g., a cat or a dog.
Basically, this is outsourcing the annotation of some data I have. For this to work, the data of all users has to be gathered and saved. It could be save by appending lines to a text file, or rows to a dataframe.
What is the right way to implement this? I couldn’t find an example that matches my use case exactly. So if you could point me to some resources, that would be perfect!
Thank you in advance!