Python的"open()"对于“找不到文件"，抛出不同的错误. -如何处理两种例外情况? [英] Python's "open()" throws different errors for "file not found" - how to handle both exceptions?

问题描述

我有一个脚本，其中提示用户键入文件名(即将打开的文件的文件名)，如果当前目录中不存在该文件，则会再次提示用户.这是简短的版本:

file = input("Type filename: ")

...
try:
    fileContent = open(filename, "r")
    ...
except FileNotFoundError:
    ...

当我在Python 3.3x的MacOS X上测试脚本时，当我有意输入错误的文件名时，它工作得很好(它在期望"下执行套件).

但是，当我想运行我的代码时 在Python 3.2x的Windows计算机上，出现错误，提示未定义"FileNotFoundError".因此，Windows上的Python 3.2认为"FileNotFoundError"是变量，并且程序因错误退出.

我发现，如果输入文件名无效，Windows上的Python 3.2会抛出"IOError".我在Python 2.7的Linux机器上对其进行了测试，它也是IOError.

我的问题是，带有

的代码

except "FileNotFoundError":

无法在Windows的Python 3.2上运行，但是如果我将其更改为

except "IOError":

它将不再在我的Mac上运行.

我该如何解决?我能想到的唯一方法就是使用 except，我通常不想要.

解决方案

在3.3中， IOError成为OSError 的别名，而FileNotFoundError是OSError的子类.所以你可以尝试

except (OSError, IOError) as e:
   ...

这将产生一个相当大的净值，并且如果不检查e.errno，您不能假定该异常是未找到文件"，但它可能涵盖了您的用例.

PEP 3151 详细讨论了更改的理由.

I have a script where a user is prompted to type a filename (of a file that is to be opened), and if the file doesn't exist in the current directory, the user is prompted again. Here is the short version:

file = input("Type filename: ")

...
try:
    fileContent = open(filename, "r")
    ...
except FileNotFoundError:
    ...

When I tested my script on my MacOS X in Python 3.3x it worked perfectly fine when I type the wrong filename on purpose (it executes the suite under "expect").

However, when I wanted to run my code on a Windows computer in Python 3.2x, I get an error that says that "FileNotFoundError" is not defined. So, Python 3.2 on Windows thinks "FileNotFoundError" is a variable and the programs quits with an error.

I figured out that Python 3.2 on Windows throws an "IOError" if the input filename is not valid. I tested it on my Linux machine in Python 2.7, and it's also an IOError.

My problem is now, that the code with

except "FileNotFoundError":

won't run on Windows's Python 3.2, but if I change it to

except "IOError":

it won't work on my Mac anymore.

How could I work around it? The only way I can think of is to use just except, which I usually don't want.

解决方案

In 3.3, IOError became an alias for OSError, and FileNotFoundError is a subclass of OSError. So you might try

except (OSError, IOError) as e:
   ...

This will cast a pretty wide net, and you can't assume that the exception is "file not found" without inspecting e.errno, but it may cover your use case.

PEP 3151 discusses the rationale for the change in detail.

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