python - 如果与 catch 子句相对应的 finally 子句包含 return 语句，如何捕获在 catch 子句中引发的异常？

Question

假设：

• TEF是一个try-except-finally块。
• 从try条款中提出了一个例外TEF
• F块的 finally 子句T包含一个返回语句
• TEF包含一个 except 子句E
• e内部引发异常E
• 我们如何e从子句F之外和子句之外捕获E？

---

如果这令人困惑，那么一些代码如下所示：

def e():
    out = "hello world"
    try:
        raise ValueError("my name is Sarah")
    except BaseException as exc:

        # HOW DO I CATCH THE FIRST OF THE FOLLOWING
        # exceptions from outside of this, current,
        # except clause?

        raise ValueError("secret info it would be good to know")
        raise AttributeError
        raise type("Hell", (Exception,), dict())()
        [0, 1, 2][99999]

        class AnythingYouCanThinkOf(Exception):
            pass

        raise AnythingYouCanThinkOf

        out = "definitely not `hello world`"
    finally:
        return out

print(e())
print("No error!!! wowza!")

上面的代码打印：

hello world
No error!!! wowza!

如果我们注释掉该行，out = "hello world"那么我们得到UnboundLocalError: local variable 'out' referenced before assignment. 但是，我仍然不确定如何恢复ValueError("secret info it would be good to know")

此外，如果您将几乎相同的代码放在函数之外e，您会得到非常不同的结果。为什么？

if True:
    out = "hello world"
    try:
        raise ValueError("my name is Bob")
    except BaseException as exc:

        # HOW DO I CATCH THE FIRST OF THE FOLLOWING
        # exceptions from outside of this, current,
        # except clause?

        raise ValueError("what is this madness?")

        class AnythingYouCanThinkOf(Exception):
            pass

        raise AnythingYouCanThinkOf

        out = "definitely not `hello world`"
    finally:
        print(out)

以上导致ValueError: what is this madness?之前未处理的异常，我们得到No error!!! wowza!

标签： pythonpython-3.xexceptiontry-catch