2nd/10_Wiki/Dev/Topic_Python/Python_Class_Properties.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-class-properties	Python Class Properties	Programming_Language	draft	conceptual		instance properties class properties 파이썬 클래스 속성		B	0.9	2026-07-04	2026-07-04			python programming w3schools class-properties	https://www.w3schools.com/python/python_class_properties.asp

Python Class Properties

🎯 한 줄 통찰 (One-line insight)

A property defined inside __init__() belongs to each individual object, but one defined directly in the class body is shared across ALL instances — changing it via ClassName.prop = value updates what every object sees, even ones created before the change. [S1]

🧠 핵심 개념 (Core concepts)

• Instance property — defined via self.x = ... inside __init__(); unique per object. [S1]
• Class property — defined directly in the class body (not inside a method); shared by ALL instances. [S1]
• Dot notation access — obj.property. [S1]
• Modifying properties — p1.age = 26 changes just that instance. [S1]
• del obj.property — deletes a property from a specific object. [S1]
• Modifying a CLASS property — Person.lastname = "Refsnes" affects every instance, including ones already created. [S1]
• Adding properties dynamically — p1.age = 25 adds a property to just that one object, not to the class. [S1]

🧩 추출된 패턴 (Extracted patterns)

• Class-level mutation is retroactive — because a class property is shared storage, not copied per instance, changing it via the class name propagates to every existing object immediately — a common source of surprise bugs if mistaken for an instance property. [S1]

📖 세부 내용 (Details)

• Instance property: class Person: def __init__(self, name, age): self.name = name; self.age = age. [S1]
• Delete a property: del p1.age — p1.name still works, but p1.age now errors. [S1]
• Class vs. instance property: class Person: species = "Human"; def __init__(self, name): self.name = name — species shared, name per-instance. [S1]
• Modifying a class property: Person.lastname = "Refsnes" — affects p1.lastname and p2.lastname both. [S1]
• Dynamic per-object addition: p1.age = 25; p1.city = "Oslo" — only affects p1. [S1]

⚖️ 모순 및 업데이트 (Contradictions & updates)

소스에서 모순되는 정보는 발견되지 않음.

🛠️ 적용 사례 (Applied in summary)

현재 발견된 실제 적용 사례가 없습니다 — 클래스 속성은 모든 인스턴스가 공유해야 하는 설정값(예: 종(species))에 쓰이고, 인스턴스 속성은 객체별 고유 데이터에 쓰인다. [S1]

💻 코드 패턴 (Code patterns)

Class property shared across all instances (Python):

class Person:
    lastname = ""  # class property
    def __init__(self, name):
        self.name = name  # instance property

p1 = Person("Linus")
p2 = Person("Emil")
Person.lastname = "Refsnes"
print(p1.lastname)  # Refsnes
print(p2.lastname)  # Refsnes

✅ 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 Class Init Method, Python Class Methods, Python Encapsulation
• 참조 맥락: 인스턴스 속성 vs 클래스 속성의 차이 — 공유 상태와 개별 상태를 구분해야 한다.

📚 출처 (Sources)

• [S1] W3Schools — Python Class Properties — https://www.w3schools.com/python/python_class_properties.asp

📝 변경 이력 (Change history)

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