python traceback.print

Python中的`traceback`模块用于处理程序运行时的异常并提供错误回溯信息。当你遇到未捕获的异常时，`traceback.print_exc()`函数可以用来显示详细的错误堆栈跟踪，帮助调试。这个函数实际上与`traceback.format_exc()`有相似的效果，但后者通常返回的是一个字符串，便于进一步处理。

**示例**：

try:
    # 这里故意引发一个异常
    raise ValueError('This is a test error')
except ValueError as e:
    # 使用traceback.print_exc()打印异常及其堆栈跟踪
    traceback.print_exc()
    # 或者使用format_exc()获得字符串形式的错误信息
    error_str = traceback.format_exc()
    print(error_str)

当这段代码执行时，你会看到类似于这样的输出（取决于实际环境）：

Traceback (most recent call last):
  File "test.py", line 3, in <module>
    raise ValueError('This is a test error')
ValueError: This is a test error

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "test.py", line 6, in <module>
    traceback.print_exc()
  File "<string>", line 1, in print_exc
ValueError: This is a test error

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

Traceback (most recent call last):
  File "test.py", line 7, in <module>
    error_str = traceback.format_exc()
  File "<string>", line 1, in format_exc
ValueError: This is a test error