flattening a list with some elements being lists

[wavic]

This is the reason I like Python - smart people (like buran) can achieve desired results with minimal and very readable piece of code. I have lot of work to do in smart part

We all are smart people. I just don't know enough. I've got RecursionError and it was said to me that it's because the strings are iterable. Then I saw how can be done for strings. I see it now too. I still don't get it why if I use a generator in the way I've done it I get this error. Yes, strings are iterable but I tried it on a small piece of data.
Something happens internally and I just don't know what it is. If one can explain it, please!