#!/usr/bin/env python3 """ Day 017 — 异常处理 API 速查表 可运行的快速参考手册，展示 Python 异常处理全部核心 API。 运行方式： python3 06-api-cheatsheet.py """ def section(title): print(f"\n{'=' * 60}") print(f" {title}") print(f"{'=' * 60}") # ═══════════════════════════════════════════════════════════════ # 1. try/except 系列 # ═══════════════════════════════════════════════════════════════ def demo_basic_structures(): """异常处理基本结构""" section("try/except 系列") # --- 基础 try/except --- try: 1 / 0 except ZeroDivisionError: print(" ✅ try/except: 基础捕获") # --- 多个 except --- try: [][5] except IndexError: print(" ✅ 多个 except: 捕获 IndexError") except KeyError: print(" 不会执行") # --- 元组捕获 --- try: {}["missing"] except (KeyError, IndexError, ValueError): print(" ✅ 元组捕获: 同时处理多种异常") # --- except as --- try: int("abc") except ValueError as e: print(f" ✅ except ... as e: 获取异常对象 → {e}") # --- else --- try: result = 10 / 2 except ZeroDivisionError: pass else: print(f" ✅ else: 无异常时执行 → 结果 = {result}") # --- finally --- try: 1 / 0 except ZeroDivisionError: print(" ✅ finally: 始终执行", end="") finally: print("（包括清理操作）") # ═══════════════════════════════════════════════════════════════ # 2. raise 系列 # ═══════════════════════════════════════════════════════════════ def demo_raise_api(): """raise 用法""" section("raise 系列") # --- 简单 raise --- try: raise ValueError("主动抛出异常") except ValueError as e: print(f" ✅ raise: 主动抛出 → {e}") # --- raise Exception("msg") --- try: raise RuntimeError("运行时错误") except RuntimeError as e: print(f" ✅ raise RuntimeError: {e}") # --- 裸 raise --- def inner(): raise ValueError("内部错误") def outer(): try: inner() except ValueError: print(" ✅ 裸 raise: 记录日志后重抛") raise try: outer() except ValueError as e: print(f" 传播到外层 → {e}") # --- raise ... from --- try: try: raise FileNotFoundError("文件缺失") except FileNotFoundError as e: raise RuntimeError("加载失败") from e except RuntimeError as e: print(f" ✅ raise ... from: {e}") print(f" 原因: {e.__cause__}") # --- raise ... from None --- try: try: raise PermissionError("无权限") except PermissionError: raise RuntimeError("访问被拒") from None except RuntimeError as e: print(f" ✅ raise ... from None: {e}") print(f" 原因: {e.__cause__} (已隐藏)") # ═══════════════════════════════════════════════════════════════ # 3. assert # ═══════════════════════════════════════════════════════════════ def demo_assert_api(): """assert 用法""" section("assert 断言") assert 1 + 1 == 2, "数学还是正确的" print(" ✅ assert True: 断言通过") try: assert 1 + 1 == 3, "数学错误！" except AssertionError as e: print(f" ✅ assert False: AssertionError → {e}") print(" ⚠️ 注意: assert 在 python -O 下禁用") # ═══════════════════════════════════════════════════════════════ # 4. sys 模块 API # ═══════════════════════════════════════════════════════════════ def demo_sys_api(): """sys.exc_info 系列""" section("sys 模块") import sys try: 1 / 0 except ZeroDivisionError: exc_type, exc_val, exc_tb = sys.exc_info() print(f" ✅ sys.exc_info():") print(f" 类型: {exc_type.__name__}") print(f" 值: {exc_val}") print(f" traceback: {exc_tb}") # ═══════════════════════════════════════════════════════════════ # 5. traceback 模块 API # ═══════════════════════════════════════════════════════════════ def demo_traceback_api(): """traceback 模块""" section("traceback 模块") import traceback try: 1 / 0 except ZeroDivisionError: tb_str = traceback.format_exc() lines = tb_str.strip().split("\n") print(f" ✅ traceback.format_exc():") for line in lines[-3:]: print(f" {line}") try: raise ValueError("测试") except ValueError as e: lines = traceback.format_exception_only(type(e), e) print(f" ✅ traceback.format_exception_only:") for line in lines: print(f" {line.strip()}") # ═══════════════════════════════════════════════════════════════ # 6. contextlib 辅助 # ═══════════════════════════════════════════════════════════════ def demo_contextlib_helpers(): """contextlib 辅助工具""" section("contextlib 辅助") from contextlib import suppress # suppress — 静默指定异常 with suppress(FileNotFoundError): open("/nonexistent/file.txt") # 不会报错 print(" ✅ contextlib.suppress: 静默指定异常") # redirect_stderr from contextlib import redirect_stderr import io f = io.StringIO() with redirect_stderr(f): try: 1 / 0 except ZeroDivisionError: print(" ✅ contextlib.redirect_stderr: 重定向错误输出", file=__import__('sys').stderr) # ═══════════════════════════════════════════════════════════════ # 7. ExceptionGroup (Python 3.11+) # ═══════════════════════════════════════════════════════════════ def demo_exception_group(): """ExceptionGroup (Python 3.11+)""" section("ExceptionGroup (3.11+)") try: exec(""" from exceptiongroup import ExceptionGroup try: raise ExceptionGroup("多个错误", [ ValueError("值1"), TypeError("类型2"), ]) except* ValueError as e: pass except* TypeError as e: pass """) except Exception as e: print(f" ℹ️ ExceptionGroup 需要 Python 3.11+") if "ExceptionGroup" in str(e): print(f" 当前 Python: {__import__('sys').version.split()[0]}") # ═══════════════════════════════════════════════════════════════ # 8. 内置异常速查 # ═══════════════════════════════════════════════════════════════ def demo_builtin_exceptions(): """常见内置异常一览""" section("常见内置异常速查") exceptions = [ ("ValueError", "int('abc')", True), ("TypeError", "1 + 'a'", True), ("IndexError", "[][10]", True), ("KeyError", "{}['k']", True), ("FileNotFoundError", "open('/x')", True), ("ZeroDivisionError", "1/0", True), ("AttributeError", "None.x", True), ("ImportError", "import nonexistent", True), ("StopIteration", "next(iter([]))", True), ("RuntimeError", "raise RuntimeError()", True), ] print(f" {'异常类型':<25s} {'触发场景':<30s} {'可捕获':<8s}") print(f" {'-'*25} {'-'*30} {'-'*8}") for name, trigger, catchable in exceptions: status = "✅" if catchable else "❌" print(f" {name:<25s} {trigger:<30s} {status:<8s}") # ═══════════════════════════════════════════════════════════════ # 入口 # ═══════════════════════════════════════════════════════════════ def main(): print("🐍 Python 异常处理 API 速查表") print() demo_basic_structures() demo_raise_api() demo_assert_api() demo_sys_api() demo_traceback_api() demo_contextlib_helpers() demo_exception_group() demo_builtin_exceptions() print() print("=" * 60) print(" ✅ API 速查完毕！") print("=" * 60) if __name__ == "__main__": main()