---
id: python-generators
title: "Python Generators"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["yield keyword", "generator expression", "파이썬 제너레이터"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.9
created_at: 2026-07-04
updated_at: 2026-07-04
review_reason: ""
merge_history: []
tags: ["python", "programming", "w3schools", "generators", "yield", "iterators"]
raw_sources: ["https://www.w3schools.com/python/python_generators.asp"]
applied_in: []
github_commit: ""
---

# [[Python Generators]]

## 🎯 한 줄 통찰 (One-line insight)
`yield` pauses a function and remembers its state instead of terminating it like `return` — letting a generator produce values one at a time on demand (e.g. an infinite Fibonacci sequence) without ever holding the full result set in memory. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Generator** — a function that can pause and resume execution; calling it returns a generator object (an iterator) without running the body yet. [S1]
- **`yield` keyword** — pauses the function, returns a value, and resumes from that exact point on the next call — unlike `return`, which terminates. [S1]
- **Memory efficiency** — values are produced on-the-fly instead of building the whole collection in memory. [S1]
- **`next()`** — manually advances a generator one step. [S1]
- **`StopIteration`** — raised when a generator has no more values to yield. [S1]
- **Generator expression** — `(x*x for x in range(5))` — same idea as list comprehension but with `()` instead of `[]`, producing a generator instead of a list. [S1]
- **`send()`** — sends a value INTO a running generator at its current yield point. [S1]
- **`close()`** — stops the generator; any `finally` block inside still runs. [S1]

## 🧩 추출된 패턴 (Extracted patterns)
- **Infinite generator via `while True`** — `def fibonacci(): a, b = 0, 1; while True: yield a; a, b = b, a+b` can generate the Fibonacci sequence forever, since nothing forces the whole sequence to materialize at once — only consumed as far as the caller iterates. [S1]
- **Priming a generator before `send()`** — the generator must be advanced once with `next(gen)` before `send()` can inject a value, since `send()` resumes execution at the currently-paused `yield`. [S1]

## 📖 세부 내용 (Details)
- Basic generator: `def my_generator(): yield 1; yield 2; yield 3; for value in my_generator(): print(value)`. [S1]
- Counting generator: `def count_up_to(n): count = 1; while count <= n: yield count; count += 1`. [S1]
- Memory-efficient large sequence: `def large_sequence(n): for i in range(n): yield i` — a million-item generator never builds a million-item list. [S1]
- Manual iteration: `gen = simple_gen(); print(next(gen)); print(next(gen))`. [S1]
- Generator expression vs list comprehension: `[x*x for x in range(5)]` vs `(x*x for x in range(5))`. [S1]
- Infinite Fibonacci generator: `def fibonacci(): a, b = 0, 1; while True: yield a; a, b = b, a + b`. [S1]
- `send()`: `gen = echo_generator(); next(gen); gen.send("Hello")`. [S1]
- `close()` with `finally`: generator's `finally` block runs on `.close()`. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
소스에서 모순되는 정보는 발견되지 않음.

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — 대용량 데이터 순회, 무한 시퀀스 생성처럼 메모리 효율이 중요한 상황에서 표준적으로 쓰인다. [S1]

## 💻 코드 패턴 (Code patterns)
Infinite Fibonacci generator (Python):
```python
def fibonacci():
    a, b = 0, 1
    while True:
        yield a
        a, b = b, a + b

gen = fibonacci()
for _ in range(100):
    print(next(gen))
```

## ✅ 검증 상태 및 신뢰도
- **상태:** draft
- **검증 단계:** conceptual
- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
- **신뢰 점수:** 0.90
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[Python Tutorial]]
- **관련 개념:** [[Python Iterators]], [[Python Recursion]], [[Python Lists Comprehension]]
- **참조 맥락:** 메모리 효율적인 지연 평가(lazy evaluation) 순회의 표준 도구.

## 📚 출처 (Sources)
- [S1] W3Schools — Python Generators — https://www.w3schools.com/python/python_generators.asp

## 📝 변경 이력 (Change history)
- 2026-07-04: Initial draft synthesized from the W3Schools "Python Generators" page (Astra wiki-curation, P-Reinforce v3.1 format).