Python 使用'；从'；语法

给定文件

errors.py

：

from traceback import format_tb, extract_tb

class MyError(Exception):
    def __init__(self, message):
        self.message = message

class MySecondError(Exception):
    def __init__(self, message):
        self.message = message

try:
    try:
        raise MyError("Something specific has happened")
    except Exception as error:
        raise MySecondError("Something general has happened") from error
except Exception as error:
    print("".join(format_tb(error.__traceback__)))

运行

python errors.py

时，输出为：

  File "errors.py", line 15, in <module>
    raise MySecondError("Something general has happened") from error

具有完整错误链的回溯和连接行的回溯（

回溯（最近一次调用）：

，

上述异常是以下异常的直接原因：

）和每个错误的字符串表示

理想情况下，我希望捕获这些输出行以将它们定向到其他位置（例如记录器）

我的一个解决方案是迭代

error.\uuuu context\uuuu

并手动添加连词：

except Exception as error:
    inner_error = error

    while inner_error:
        if inner_error is not error:
            print("\nThe above exception was the direct cause of the following exception:\n")

        print("Traceback (most recent call last):")
        print("".join(format_tb(inner_error.__traceback__) + [ str(error) ])) 
        inner_error = inner_error.__context__

这是可行的，但它是有漏洞的，我更喜欢使用一些已经处理了这个问题的标准库模块。

您想使用这个函数：

from traceback import format_tb, format_exception

class MyError(Exception):
    def __init__(self, message):
        self.message = message

class MySecondError(Exception):
    def __init__(self, message):
        self.message = message

try:
    try:
        raise MyError("Something specific has happened")
    except Exception as error:
        raise MySecondError("Something general has happened") from error
except Exception as error:
    print("".join(format_exception(error.__class__, error, error.__traceback__)))

给出：

$ python3 /tmp/a.py 
Traceback (most recent call last):
  File "/tmp/a.py", line 13, in <module>
    raise MyError("Something specific has happened")
MyError: Something specific has happened

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

Traceback (most recent call last):
  File "/tmp/a.py", line 15, in <module>
    raise MySecondError("Something general has happened") from error
MySecondError: Something general has happened

$python3/tmp/a.py
回溯（最近一次呼叫最后一次）：
文件“/tmp/a.py”，第13行，在
提出我的错误（“发生了特定的事情”）
迈罗：发生了一些特别的事情
上述异常是以下异常的直接原因：
回溯（最近一次呼叫最后一次）：
文件“/tmp/a.py”，第15行，在
从错误中引发MySecondError（“发生了一般性的事情”）
迈斯康德罗：发生了一些一般性的事情

---

如果您指定

chain=False

此函数将不打印连环异常，而只打印最后一个异常。

谢谢，在浏览

回溯

模块文档时应该会发现这一点

$ python3 /tmp/a.py 
Traceback (most recent call last):
  File "/tmp/a.py", line 13, in <module>
    raise MyError("Something specific has happened")
MyError: Something specific has happened

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

Traceback (most recent call last):
  File "/tmp/a.py", line 15, in <module>
    raise MySecondError("Something general has happened") from error
MySecondError: Something general has happened