Question

尝试读取文件的Pythonic方法是什么？如果此读取会引发异常回退以读取备用文件？

这是我编写的示例代码，它使用嵌套的try - except块。这是pythonic：

try:
    with open(file1, "r") as f:
        params = json.load(f)
except IOError:
    try:
        with open(file2, "r") as f:
            params = json.load(f)
    except Exception as exc:
        print("Error reading config file {}: {}".format(file2, str(exc)))
        params = {}
except Exception as exc:
    print("Error reading config file {}: {}".format(file1, str(exc)))
    params = {}

Answer 1

对于两个文件，这种方法在我看来足够好。

如果你有更多的文件需要后备，我会选择循环：

for filename in (file1, file2):
    try:
        with open(filename, "r") as fin:
            params = json.load(f)
        break
    except IOError:
        pass
    except Exception as exc:
        print("Error reading config file {}: {}".format(filename, str(exc)))
        params = {}
        break
else:   # else is executed if the loop wasn't terminated by break
    print("Couldn't open any file")
    params = {}

Answer 2

您可以先检查file1是否存在，然后决定打开哪个文件。它会缩短代码并避免重复try -- catch子句。我相信它更加pythonic，但请注意，您需要在模块中import os才能使其工作。它可以是：

fp = file1 if os.path.isfile(file1) else file2
if os.path.isfile(fp):
    try:
        with open(fp, "r") as f:
            params = json.load(f)
    except Exception as exc:
        print("Error reading config file {}: {}".format(fp, str(exc)))
            params = {}
else:
    print 'no config file'

Answer 3

虽然我不确定这是否是pythonic，但也许是这样的：

file_to_open = file1 if os.path.isfile(file1) else file2

Pythonic尝试读取文件的方法，以及异常回退到备用文件的情况

3 个答案: