如何在python中的一个块中编写多个try语句？

Question

我想要做:

try:
    do()
except:
    do2()
except:
    do3()
except:
    do4()

如果do()失败,则执行do2(),如果do2()也失败,则执行do3()等等.

最好的祝福

Answer 1

如果你真的不关心异常,你可以循环遍历案例直到你成功:

for fn in (do, do2, do3, do4):
    try:
        fn()
        break
    except:
        continue

这至少避免了每个案例都必须缩进一次.如果不同的函数需要不同的参数,你可以使用functools.partial在循环之前"填充"它们.

Answer 2

我会first()为此编写一个快速包装函数.

用法:value = first([f1, f2, f3, ..., fn], default='All failed')

#!/usr/bin/env


def first(flist, default=None):

    """ Try each function in `flist` until one does not throw an exception, and
    return the return value of that function. If all functions throw exceptions,
    return `default` 

    Args: 
        flist - list of functions to try
        default - value to return if all functions fail

    Returns:
        return value of first function that does not throw exception, or
        `default` if all throw exceptions.

    TODO: Also accept a list of (f, (exceptions)) tuples, where f is the
    function as above and (exceptions) is a tuple of exceptions that f should
    expect. This allows you to still re-raise unexpected exceptions.
    """

    for f in flist:
        try:
            return f()
        except:
            continue
    else:
        return default

# Testing.

def f():
    raise TypeError

def g():
    raise IndexError

def h():
    return 1


# We skip two exception-throwing functions and return value of the last.
assert first([f, g, h]) == 1

assert first([f, g, f], default='monty') == 'monty'

Answer 3

这似乎是一件非常奇怪的事情,但我可能会在没有异常的情况下循环使用函数并突破:

for func in [do, do2, do3]:
    try:
        func()
    except Exception:
        pass
    else:
        break