What is yield from and when to use it?

Question

Accepted Answer

**yield from** delegates yielding to a sub-generator. Simplifies generator composition.

```python
# Without yield from
def flatten_manual(nested):
    for item in nested:
        if isinstance(item, list):
            for sub in flatten_manual(item):
                yield sub
        else:
            yield item

# With yield from
def flatten(nested):
    for item in nested:
        if isinstance(item, list):
            yield from flatten(item)  # Delegates to sub-generator
        else:
            yield item

data = [1, [2, 3], [4, [5, 6]]]
print(list(flatten(data)))  # [1, 2, 3, 4, 5, 6]
```

**Using with iterables:**
```python
def chain(*iterables):
    for iterable in iterables:
        yield from iterable

result = list(chain([1, 2], [3, 4], [5]))
# [1, 2, 3, 4, 5]
```

**Benefits:**
- Cleaner code (removes inner for-loop).
- Better performance.
- Transparent exception handling.

Python: What is yield from and when to use it?