Problem about yield, please help!!

[cls0724]

I am still new to Python and i come across the below sample from my textbook that confuses me quite a lot.

[u]def flatten(nested, indent=""):
  try:
    print(indent, "Going to iterate over", nested)
    for sublist in nested:
      print(indent, "Going to iterate over flattening of",sublist)
      for element in flatten(sublist, indent+"  "):
        print(indent, "Yielding", element)
        yield element
  except TypeError:
    print(indent, "Type Error!  Yielding", nested)
    yield nested[/u]

The above code is to flatten a list. I understand how a list is flattened till you reach a number.
Then you reach Type Error.

However, i dun understand the next step when the

yield nested

then jump to

for element in flatten

.

I can comprehend the logic in between. I thought once you reached TypeError then it's the end of this loop. Why it will lead back to

for element in flatten

.

Thanks!