Can I make the first element in a generator return something special/different?

Question

If I have a generator that sequentially returns items in a list, is there any way to make the first return something different? e.g. if the list is ['apple', 'bag', 'cat', 'dog'...], could I make the generator yield

'apple is the first item'
'bag'
'cat'
'dog'

etc?

For some context: I am trying to stream a large file through flask using a generator object.

Answer 1

You can consume the first element, modify it and yield it; then yield the rest.

def mark_first_item(it):
    first = next(it)
    yield f"{first} is the first item"
    yield from it

stuff = ['apple', 'bag', 'cat', 'dog']
print(list(mark_first_item(iter(stuff))))

Answer 2

You can try enumerate

items = ['apple', 'bag', 'cat', 'dog']
genItems = (f"{v} is first element" if i==0 else v for i, v in enumerate(items))