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86 lines
3.4 KiB
Markdown
86 lines
3.4 KiB
Markdown
---
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id: python-booleans
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title: "Python Booleans"
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category: "Programming_Language"
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status: "draft"
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verification_status: "conceptual"
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canonical_id: ""
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aliases: ["bool()", "truthiness", "파이썬 불리언"]
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duplicate_of: ""
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source_trust_level: "B"
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confidence_score: 0.9
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created_at: 2026-07-04
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updated_at: 2026-07-04
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review_reason: ""
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merge_history: []
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tags: ["python", "programming", "w3schools", "boolean", "truthiness"]
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raw_sources: ["https://www.w3schools.com/python/python_booleans.asp"]
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applied_in: []
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github_commit: ""
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---
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# [[Python Booleans]]
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## 🎯 한 줄 통찰 (One-line insight)
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Almost every Python value is truthy by default — only a small, fixed set (empty collections, 0, "", None, False, and objects whose `__len__` returns 0) evaluates to False. [S1]
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## 🧠 핵심 개념 (Core concepts)
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- **Boolean** — represents one of two values: True or False. [S1]
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- **`bool()` function** — evaluates any value/variable and returns True or False. [S1]
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- **Most values are True** — any non-empty string, any non-zero number, any non-empty list/tuple/set/dict. [S1]
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- **Falsy exceptions** — `()`, `[]`, `{}`, `""`, `0`, `None`, `False`. [S1]
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- **Custom falsy objects** — an object from a class whose `__len__` returns 0 (or False) also evaluates to False. [S1]
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- **Functions can return booleans** — including built-ins like `isinstance()`. [S1]
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## 🧩 추출된 패턴 (Extracted patterns)
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- **`__len__`-based falsiness** — Python's truthiness protocol extends to custom classes via `__len__`, meaning "empty-like" custom objects behave like empty built-in collections. [S1]
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## 📖 세부 내용 (Details)
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- Comparison expressions return booleans: `print(10 > 9); print(10 == 9); print(10 < 9)`. [S1]
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- Truthy check: `bool("Hello") # True`, `bool(15) # True`. [S1]
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- Falsy check: `bool(False); bool(None); bool(0); bool(""); bool(()); bool([]); bool({})`. [S1]
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- Custom falsy via `__len__`: [S1]
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```python
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class myclass():
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def __len__(self):
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return 0
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myobj = myclass()
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print(bool(myobj)) # False
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```
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- `isinstance()` returns a boolean: `print(isinstance(x, int))`. [S1]
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## ⚖️ 모순 및 업데이트 (Contradictions & updates)
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소스에서 모순되는 정보는 발견되지 않음.
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## 🛠️ 적용 사례 (Applied in summary)
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현재 발견된 실제 적용 사례가 없습니다 — if 조건문/논리 연산자 챕터 전체가 이 불리언 평가 규칙을 전제로 한다. [S1]
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## 💻 코드 패턴 (Code patterns)
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Custom class controlling its own truthiness (Python):
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```python
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class myclass():
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def __len__(self):
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return 0
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myobj = myclass()
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print(bool(myobj)) # False
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```
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## ✅ 검증 상태 및 신뢰도
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- **상태:** draft
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- **검증 단계:** conceptual
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- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
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- **신뢰 점수:** 0.90
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- **중복 검사 결과:** 신규 생성 (New discovery)
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## 🔗 지식 그래프 (Knowledge Graph)
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- **상위/루트:** [[Python Tutorial]]
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- **관련 개념:** [[Python If Else]], [[Python Operators Logical]], [[Python Operators Comparison]]
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- **참조 맥락:** 조건문/논리 연산의 기초 — if 문/while 루프의 조건 평가 방식을 정의.
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## 📚 출처 (Sources)
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- [S1] W3Schools — Python Booleans — https://www.w3schools.com/python/python_booleans.asp
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## 📝 변경 이력 (Change history)
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- 2026-07-04: Initial draft synthesized from the W3Schools "Python Booleans" page (Astra wiki-curation, P-Reinforce v3.1 format).
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