sys.exc_info() 的目的是什么？

Question

我想了解两者的区别：

try:
    raise Exception("wat")
except Exception:
    extype, exc, tb = sys.exc_info()
    traceback.print_exception(extype, exc, tb)

和：

try:
    raise Exception("wat")
except Exception as exc:
    extype = type(exc)
    tb = exc.__traceback__
    traceback.print_exception(extype, exc, tb)

是否存在 type(exc) 和 exc.__traceback__ 与 sys.exc_info() 编辑的值 return 不同的情况？如果不是，我应该什么时候更喜欢一个？当我对此进行测试时 (Python 3.7)，returned 对象在引用上是相同的。

查看 CPython 中 exc_info() 的实现，第一个 return 值（异常类型）似乎是通过调用 PyExceptionInstance_Class 获得的，它是与 type(exc) 完全相同。但是，我找不到回溯是如何设置的。

（FWIW 我知道 traceback.print_exc() shorthand，这与这个问题无关）

Answer 1

__traceback__ 属性仅在 Python 3.0 之后可用，因此如果您希望使代码与 Python 2 兼容，则应改用 sys.exc_info() ;否则，根据 PEP-3134，__traceback__ 属性的引入确实意味着完全取代 sys.exc_info()，并可能弃用它：

In today's Python implementation, exceptions are composed of three parts: the type, the value, and the traceback. The sys module, exposes the current exception in three parallel variables, exc_type, exc_value, and exc_traceback, the sys.exc_info() function returns a tuple of these three parts, and the raise statement has a three-argument form accepting these three parts. Manipulating exceptions often requires passing these three things in parallel, which can be tedious and error-prone. Additionally, the except statement can only provide access to the value, not the traceback. Adding the __traceback__ attribute to exception values makes all the exception information accessible from a single place.

sys.exc_info() 的目的是什么？

What is the purpose of sys.exc_info()?

python

cpython

exception