What is the difference between a generator and an iterator?

Question

Accepted Answer

**Iterator** is any object with `__iter__` and `__next__`. **Generator** is a special iterator created with `yield`.

```python
# Iterator — any object with __iter__ and __next__
class CountUp:
    def __init__(self, stop):
        self.stop = stop
        self.current = 0

def __iter__(self):
        return self

def __next__(self):
        if self.current >= self.stop:
            raise StopIteration
        self.current += 1
        return self.current

# Generator — simpler, uses yield
def count_up(stop):
    current = 0
    while current < stop:
        current += 1
        yield current

# Both work the same way
for n in CountUp(5):
    print(n)  # 1, 2, 3, 4, 5

for n in count_up(5):
    print(n)  # 1, 2, 3, 4, 5
```

**Advantages of generators:**
- Simpler syntax (yield vs __iter__ + __next__).
- Automatic state management.
- Memory efficient.
- Can use `send()`, `throw()`, `close()`.

Python: What is the difference between a generator and an iterator?