How to Delegate Iteration to a Subgenerator with yield from in Python

Use yield from to delegate iteration from one generator to a subgenerator, flattening nested generator output into a single sequence.

Easy Python 3.9+ Aug 9, 2026 Comprehensions & generators 13 views 0 copies

generators yield-from delegation iteration subgenerator

Python code

15 lines

Python 3.9+

def subgenerator():
    yield "first"
    yield "second"
    yield "third"


def delegate():
    yield "before delegation"
    yield from subgenerator()
    yield "after delegation"


if __name__ == "__main__":
    for item in delegate():
        print(item)

Output

stdout

before delegation
first
second
third
after delegation

How it works

The yield from expression forwards yielded values from the subgenerator to the caller, making the outer generator behave as if its body were spliced into the delegating generator. It also forwards send() and throw() calls, so the delegation is transparent for advanced generator protocols. This pattern reduces nested loops and keeps generator code readable when composing multiple generators.

Common mistakes

Using `yield from` with a non-iterable argument instead of a generator/iterable
Forgetting that `yield from` can only be used inside a generator function
Confusing `yield from` with `return from` — it never returns the subgenerator's value

Variations

Chain multiple generators: `yield from gen1; yield from gen2`
Use `yield from` with lists or other iterables to flatten them into the generator stream

Real-world use cases

Composing multiple pipeline stages where each stage is a generator that processes data incrementally.
Building a CLI tool that concatenates multiple log files by delegating to per-file parsers.
Implementing a recursive generator that yields items from nested tree structures with minimal boilerplate.

How to Delegate Iteration to a Subgenerator with yield from in Python

Python code

Output

How it works

Common mistakes

Variations

Real-world use cases

More from Comprehensions & generators

Tutorials

Quizzes

Python code

Output

How it works

Common mistakes

Variations

Real-world use cases

More from Comprehensions & generators

Keep learning

Tutorials

Quizzes