如何使用 Python 正确传播错误消息

Question

我对正确的 Python 错误处理有点陌生，我很难找到如何处理几种方法链中错误的野兽方法。

我有 3 种方法 - a、b、c。 a正在呼叫b，b正在呼叫c。如何将错误从方法 c 传播回方法 a 这样我就可以，例如存储在某个地方还是在 API 响应期间返回？

示例代码：

def c(x, y):
  try:
    return int(x), int(y)
  except Exception:
    print("x or y is probably not a number")

def b(x, y):
  try:
    x, y = c(x, y)
    return x + y
  except Exception:
    print("issue during sum of x and y")

def a(x, y):
  try:
    return b(x, y)
  except Exception:
    print("some unknown error occured")

 
result = a(4, 5)
result = a('test', 10)

上面的代码在某些情况下会打印出一些错误。很明显，您可以在控制台中看到这些错误，但是以后如何处理这些“错误”消息呢？例如，如果从另一个模块调用方法a，我想返回它们并存储。现在 result 的值为 None，以防发生错误。

换句话说，我想“以某种方式”从方法c 直接跳回到方法a 并显示响应。

像这样返回错误消息本身是正确的方法吗？

def c(x, y):
  try:
    return int(x), int(y)
  except Exception:
    return "x or y is probably not a number"

Answer 1

错误传播

如果你想传播异常，你可以使用 use from 子句

所有信息都可以在这里查看https://docs.python.org/3/reference/simple_stmts.html#grammar-token-raise-stmt

def c(x, y):
    try:
        return int(x), int(y)
    except Exception as e:   
        msg = "x or y is probably not a number"
        raise Exception(msg) from e   

def b(x, y):
    try:
        x, y = c(x, y)
        return x + y 
    except Exception as e:
        msg = "issue during sum of x and y"
        raise Exception(msg) from e   

def a(x, y):
    try:
        return b(x, y)
    except Exception as e:
        msg = "some unknown error occured"
        raise Exception(msg) from e    

result = a('test', 10)

这样您就可以一直追踪所有错误及其来源

这是输出： https://i.stack.imgur.com/2ho5K.png

回溯抑制

如果你想抑制你需要使用的错误的所有回溯 from None

def a(x, y):
    try:
        return b(x, y)
    except Exception as e:
        msg = "some unknown error occured"
        raise Exception(msg) from None   

现在运行代码将抑制所有以前的错误，这是输出： https://i.stack.imgur.com/loFis.png

将错误恢复为字符串

到目前为止，捕获我发现的错误的最佳方法，感谢@anton 的 cmets，他建议使用 traceback 是使用装饰器

from functools import wraps, partial
import traceback  
import sys


def error_handler(func=None, *, raise_error=False):
    if not func:
        return partial(error_handler, raise_error=raise_error)
    
    @wraps(func)
    def func_exectutor(*args, **kwargs):
        try:
            out = func(*args, **kwargs)
            exception = False
        except Exception as error:
            exception = True
            string = ''.join(traceback.format_exception(None, error, error.__traceback__))
            out = string, error
        finally:
            if not exception:
                return out
            else:
                if raise_error:
                    raise out[1]
                else:
                    return out[0]
    return func_exectutor

装饰功能后：

@error_handler(raise_error=False)
def a(x, y):
    try:
        return b(x, y)
    except Exception as e:
        msg = "some unknown error occured"
        raise Exception(msg) from e   

如果失败，该函数的输出是一个字符串，其中包含所有可能发生的错误的回溯。如果不是，则输出是预期的

a(4, 10)
>>> 14

a('test', 10)
>>> 'Traceback (most recent call last):
  File "/tmp/ipykernel_60630/2959315277.py", line 3, in c
    return int(x), int(y)
ValueError: invalid literal for int() with base 10: 'test'

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

Traceback (most recent call last):
  File "/tmp/ipykernel_60630/2959315277.py", line 10, in b
    x, y = c(x, y)
  File "/tmp/ipykernel_60630/2959315277.py", line 6, in c
    raise Exception(msg) from e
Exception: x or y is probably not a number

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

Traceback (most recent call last):
  File "/tmp/ipykernel_60630/2959315277.py", line 19, in a
    return b(x, y)
  File "/tmp/ipykernel_60630/2959315277.py", line 14, in b
    raise Exception(msg) from e
Exception: issue during sum of x and y

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

Traceback (most recent call last):
  File "/tmp/ipykernel_60630/879165569.py", line 13, in func_exectutor
    out = func(*args, **kwargs)
  File "/tmp/ipykernel_60630/2959315277.py", line 22, in a
    raise Exception(msg) from e
Exception: some unknown error occured
'