traceback

traceback 模块用于提取、格式化和打印 Python 程序的堆栈回溯信息。它与 sys.exc_info() 配合，提供了对异常链和调用栈的完整控制。

traceback

打印异常信息

import traceback

def func_a():
    func_b()

def func_b():
    func_c()

def func_c():
    raise ValueError("something went wrong")

try:
    func_a()
except:
    traceback.print_exc()
"""
Traceback (most recent call last):
  File "...", line 13, in <module>
    func_a()
  File "...", line 4, in func_a
    func_b()
  File "...", line 7, in func_b
    func_c()
  File "...", line 10, in func_c
    raise ValueError("something went wrong")
ValueError: something went wrong
"""

捕获异常为字符串

import traceback

def risky_operation():
    return 1 / 0

try:
    risky_operation()
except Exception:
    error_msg = traceback.format_exc()
    print(type(error_msg))  # <class 'str'>
    # 可以写入日志、发送到监控系统等
    print(error_msg)

提取结构化的堆栈信息

import traceback
import sys

def deep_call():
    raise RuntimeError("deep error")

def middle():
    deep_call()

def top():
    middle()

try:
    top()
except:
    tb = traceback.extract_tb(sys.exc_info()[2])
    for frame in tb:
        print(f"{frame.filename}:{frame.lineno} in {frame.name}")
        print(f"  -> {frame.line}")

打印当前调用栈（不抛异常）

import traceback

def show_stack():
    print("当前调用栈:")
    traceback.print_stack()

def caller():
    show_stack()

caller()

异常链（Exception Chaining）

import traceback

def load_config():
    try:
        open("nonexistent.toml")
    except FileNotFoundError as e:
        raise RuntimeError("配置加载失败") from e

try:
    load_config()
except RuntimeError:
    traceback.print_exc()
"""
Traceback (most recent call last):
  ...
FileNotFoundError: [Errno 2] No such file or directory: 'nonexistent.toml'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  ...
RuntimeError: 配置加载失败
"""

TracebackException 对象

Python 3.5+ 提供了面向对象的 TracebackException 类，适合延迟格式化和序列化。

import traceback
import sys

try:
    eval("1/0")
except:
    te = traceback.TracebackException(*sys.exc_info())
    print("异常类型:", te.exc_type.__name__)
    print("异常消息:", str(te))
    print("格式化输出:")
    for line in te.format():
        print(line, end="")

tip

大型系统（训练框架、推理服务）中，精确的异常追踪至关重要。traceback.format_exc() 常被用于：

• 将错误信息写入结构化日志
• 在分布式训练中收集各节点的异常信息
• 在 API 服务中返回有意义的错误响应