Is it possible to iterate over a generator twice? Why?

A generator in Python is an iterator that generates values "on the fly" and maintains its state between calls. It can only be traversed once because after a complete iteration, the generator is considered exhausted and cannot be restarted.

If you try to iterate over the generator a second time, it will immediately finish without yielding any elements.

Example:

def gen():
    yield 1
    yield 2
    yield 3

g = gen()
print(list(g))  # [1, 2, 3]
print(list(g))  # [] — generator is already exhausted

To iterate over the data multiple times, you need to either create a new generator or use a collection that stores all elements (for example, a list).