如何在python中的一个块中编写多个try语句？
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How to write multiple try statements in one block in python?
提问by alwbtc
I want to do:
我想要做：
try:
do()
except:
do2()
except:
do3()
except:
do4()
If do() fails, execute do2(), if do2() fails too, exceute do3() and so on.
如果 do() 失败，则执行 do2()，如果 do2() 也失败，则执行 do3() 等等。
best Regards
此致
采纳答案by Triptych
I'd write a quick wrapper function first()for this.
我会first()为此编写一个快速包装函数。
usage: value = first([f1, f2, f3, ..., fn], default='All failed')
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'
回答by alexvassel
You should specify the type of the exception you are trying to catch each time.
您应该指定每次尝试捕获的异常类型。
try:
do()
except TypeError: #for example first one - TypeError
do_2()
except KeyError: #for example second one - KeyError
do_3()
and so on.
等等。
回答by Fredrik H??rd
If you really don't care about the exceptions, you could loop over cases until you succeed:
如果你真的不关心异常，你可以循环遍历案例直到成功：
for fn in (do, do2, do3, do4):
try:
fn()
break
except:
continue
This at least avoids having to indent once for every case. If the different functions need different arguments you can use functools.partial to 'prime' them before the loop.
这至少避免了必须为每个案例缩进一次。如果不同的函数需要不同的参数，您可以使用 functools.partial 在循环之前“准备”它们。
回答by gaqzi
It seems like a really odd thing to want to do, but I would probably loop over the functions and break out when there were no exception raised:
这似乎是一件很奇怪的事情，但我可能会循环遍历这些函数并在没有出现异常时中断：
for func in [do, do2, do3]:
try:
func()
except Exception:
pass
else:
break
回答by sparrow
Here is the simplest way I found, just embed the try under the previous except.
这是我找到的最简单的方法，只需将 try 嵌入到之前的 except 之下。
try:
do()
except:
try:
do2()
except:
do3()
回答by Raghu nathan
import sys
try:
f = open('myfile.txt')
s = f.readline()
i = int(s.strip())
except OSError as err:
print("OS error: {0}".format(err))
except ValueError:
print("Could not convert data to an integer.")
except:
print("Unexpected error:", sys.exc_info()[0])
raise
