2nd/10_Wiki/Topic_Programming/Topic_Python/Python_Iterators.md

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id	title	category	status	verification_status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	created_at	updated_at	review_reason	merge_history	tags	raw_sources	applied_in	github_commit
python-iterators	Python Iterators	Programming_Language	draft	conceptual		iterator protocol __iter__ __next__ 파이썬 이터레이터		B	0.9	2026-07-04	2026-07-04			python programming w3schools iterators iterable	https://www.w3schools.com/python/python_iterators.asp

Python Iterators

🎯 한 줄 통찰 (One-line insight)

An iterable (list, tuple, string, etc.) is a container you can get an iterator FROM via iter(); a custom class becomes its own iterator by implementing __iter__() (return self) and __next__() (return the next value, raising StopIteration to terminate). [S1]

🧠 핵심 개념 (Core concepts)

• Iterator — an object implementing the iterator protocol (__iter__() and __next__()); contains a countable number of values. [S1]
• Iterable vs. iterator — lists/tuples/dicts/sets are iterable (have an iter() method to GET an iterator); the iterator itself is what next() advances. [S1]
• iter() — returns an iterator from an iterable object. [S1]
• next() — advances the iterator one step, returning the next value. [S1]
• for loop internals — a for loop actually creates an iterator object internally and calls next() on each pass. [S1]
• Custom iterator class — implement __iter__() (must return the iterator object itself) and __next__() (must return the next value in sequence). [S1]
• StopIteration — raised inside __next__() to signal the end, preventing infinite iteration in a for loop. [S1]

🧩 추출된 패턴 (Extracted patterns)

• Without StopIteration, custom iterators run forever in a for loop — the example shows that a __next__() with no terminating condition would loop forever if placed in a for loop (unlike manual next() calls, which just stop when you stop calling them). [S1]

📖 세부 내용 (Details)

• Get iterator from a tuple: mytuple = ("apple","banana","cherry"); myit = iter(mytuple); print(next(myit)). [S1]
• Custom iterator class: [S1]

class MyNumbers:
    def __iter__(self):
        self.a = 1
        return self
    def __next__(self):
        x = self.a
        self.a += 1
        return x

• With StopIteration to prevent infinite loop: if self.a <= 20: ... else: raise StopIteration. [S1]

⚖️ 모순 및 업데이트 (Contradictions & updates)

소스에서 모순되는 정보는 발견되지 않음.

🛠️ 적용 사례 (Applied in summary)

현재 발견된 실제 적용 사례가 없습니다 — Python Generators 챕터의 yield가 이 이터레이터 프로토콜을 훨씬 간결하게 구현하는 대안이다. [S1]

💻 코드 패턴 (Code patterns)

Custom iterator with a StopIteration terminating condition (Python):

class MyNumbers:
    def __iter__(self):
        self.a = 1
        return self
    def __next__(self):
        if self.a <= 20:
            x = self.a
            self.a += 1
            return x
        else:
            raise StopIteration

myclass = MyNumbers()
myiter = iter(myclass)
for x in myiter:
    print(x)

✅ 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 Generators, Python For Loops, Python Classes
• 참조 맥락: for 루프가 내부적으로 사용하는 프로토콜 — Generators가 이를 간결화한 대안이다.

📚 출처 (Sources)

• [S1] W3Schools — Python Iterators — https://www.w3schools.com/python/python_iterators.asp

📝 변경 이력 (Change history)

• 2026-07-04: Initial draft synthesized from the W3Schools "Python Iterators" page (Astra wiki-curation, P-Reinforce v3.1 format).