---
id: python-recursion
title: "Python Recursion"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["recursive function", "base case", "파이썬 재귀"]
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", "recursion"]
raw_sources: ["https://www.w3schools.com/python/python_recursion.asp"]
applied_in: []
github_commit: ""
---

# [[Python Recursion]]

## 🎯 한 줄 통찰 (One-line insight)
Every recursive function needs a base case that stops the recursion — without one, it calls itself forever and hits Python's default ~1000-call recursion limit, raising a stack-related error. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Recursion** — a function calling itself; useful for looping through data to reach a result. [S1]
- **Base case** — the condition that stops the recursion. [S1]
- **Recursive case** — the function calling itself with a modified (usually smaller) argument. [S1]
- **Risk** — without a base case, infinite recursion causes a stack overflow / excess memory/CPU use. [S1]
- **`sys.getrecursionlimit()` / `sys.setrecursionlimit()`** — inspect/raise the default recursion depth limit (~1000), with a caution against raising it carelessly. [S1]

## 🧩 추출된 패턴 (Extracted patterns)
- **List recursion via slicing** — processing a list recursively (`sum_list`, `find_max`) typically uses `numbers[1:]` to shrink the list each call, with an empty-list or single-element check as the base case. [S1]
- **Prefer iteration for very deep recursion** — the source explicitly recommends switching to iteration rather than raising the recursion limit for cases needing very deep recursion. [S1]

## 📖 세부 내용 (Details)
- Simple countdown: `def countdown(n): if n <= 0: print("Done!") else: print(n); countdown(n - 1)`. [S1]
- Factorial with explicit base/recursive case: `def factorial(n): if n == 0 or n == 1: return 1; else: return n * factorial(n - 1)`. [S1]
- Fibonacci via recursion: `def fibonacci(n): if n <= 1: return n; else: return fibonacci(n-1) + fibonacci(n-2)`. [S1]
- List sum via recursion: `def sum_list(numbers): if len(numbers) == 0: return 0; else: return numbers[0] + sum_list(numbers[1:])`. [S1]
- Recursion limit: `import sys; print(sys.getrecursionlimit())`. [S1]

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

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — 트리/그래프 탐색처럼 자연스럽게 재귀적인 구조를 다룰 때 표준적으로 쓰인다. [S1]

## 💻 코드 패턴 (Code patterns)
Base case and recursive case (Python):
```python
def factorial(n):
    if n == 0 or n == 1:      # base case
        return 1
    else:                      # recursive case
        return n * factorial(n - 1)
```

## ✅ 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 Functions]], [[Python Generators]], [[Python Lists]]
- **참조 맥락:** 자기 자신을 호출하는 함수 패턴 — 반드시 base case가 있어야 안전하다.

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

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