Какова роль конструкции yield from в Python?

The yield from construct is used to delegate control of iteration from one generator (the delegating generator) to another generator or iterator (the subgenerator).

Main features of yield from:

• Simplifies code reading: Replaces more complex logic of handling the subgenerator with explicit send and throw.
• Automatically handles exceptions: Exceptions sent to the delegating generator are passed to the subgenerator.
• Automatically handles the return value: The value returned by the subgenerator (via return) becomes the value of the yield from expression.

# Example without yield from (more complex)
def subgenerator_manual():
    yield 1
    yield 2
    return "Manual result"

def delegator_manual():
    sub = subgenerator_manual()
    try:
        value = next(sub)
        while True:
            try:
                sent = yield value
                value = sub.send(sent)
            except StopIteration as e:
                return e.value
    except StopIteration as e:
        return e.value

# Example with yield from (simpler)
def subgenerator_yield_from():
    yield 10
    yield 20
    return "Yield from result"

def delegator_yield_from():
    result = yield from subgenerator_yield_from()
    print(f"Subgenerator returned: {result}") # Displays the value returned by the subgenerator
    yield 30

# Usage
g_manual = delegator_manual()
print(list(g_manual))

g_yield_from = delegator_yield_from()
print(list(g_yield_from))

In the example with yield from, the main generator delegator_yield_from delegates iteration to subgenerator_yield_from. When subgenerator_yield_from finishes with a return, the returned value ("Yield from result") is assigned to the variable result in delegator_yield_from.