Python 单行异常处理
在Python中,可以使用一行程序以简单直观的方式使用特殊条件(如默认值或条件)设置值Python 单行异常处理,python,python-3.x,exception,exception-handling,Python,Python 3.x,Exception,Exception Handling,在Python中,可以使用一行程序以简单直观的方式使用特殊条件(如默认值或条件)设置值 result = 0 or "Does not exist." # "Does not exist." result = "Found user!" if user in user_list else "User not found." 是否可以编写一个捕获异常的类似语句 from json import loads result = loads('{"value": true}') or "Oh n
result = 0 or "Does not exist." # "Does not exist."
result = "Found user!" if user in user_list else "User not found."
是否可以编写一个捕获异常的类似语句
from json import loads
result = loads('{"value": true}') or "Oh no, explosions occurred!"
# {'value': True}
result = loads(None) or "Oh no, explosions occurred!"
# "Oh no, explosions occurred!" is desired, but a TypeError is raised.
在python中不可能执行一行异常处理语句。可以编写一个函数来实现这一点
def safe_execute(default, exception, function, *args):
try:
return function(*args)
except exception:
return default
用法示例:
from json import loads
safe_execute("Oh no, explosions occurred!", TypeError, loads, None)
# Returns "Oh no, explosions occurred!"
safe_execute("Huh?", TypeError, int, "10")
#Returns 10
支持多个参数
from operator import div
safe_execute(
"Divsion by zero is invalid.",
ZeroDivisionError,
div, 1, 0
)
# Returns "Divsion by zero is invalid."
safe_execute(
"Divsion by zero is invalid.",
ZeroDivisionError,
div, 1, 1
)
# Returns 1.
错误捕获过程仍可能被中断:
from time import sleep
safe_execute(
"Panic!",
Exception,
sleep, 8
)
# Ctrl-c will raise a KeyboardInterrupt
from sys import exit
safe_execute("Failed to exit!", Exception, exit)
# Exits the Python interpreter
如果此行为不受欢迎,请使用BaseException
:
from time import sleep
safe_execute("interrupted",
BaseException,
sleep, 8)
#Pressing Ctrl-c will return "interrupted"
from sys import exit
safe_execute("Naughty little program!",
BaseException,
exit)
#Returns "Naughty little program!"
可以在一行中使用exec:
parse_float = lambda x, y=exec("def f(s):\n try:\n return float(s)\n except: return None"): f(x)
您可以使用
contextlib
来抑制异常。如果你喜欢危险地生活,你可以抑制BaseException
,这将抑制所有内置异常(可能是个坏主意)。或者你可以选择一个与你的代码相关的安全代码,比如TypeError
示例:
from contextlib import suppress
# this will execute right along
with suppress(BaseException): fhasldjkfhsa345315
# even raising an Exception will fly just fine
with suppress(BaseException): raise NameError
# correct code will execute just fine
x=5
with suppress(BaseException): x+=2
print(x) # prints 7
# and in your example:
from json import loads
pleasure = suppress(TypeError) # so each line rolls off the tongue :)
with pleasure: result = loads('{"value": True}')
print(result) # prints {'value': True}
with pleasure: result = loads(None)
print(result) # prints {'value': True} because result never changed
为什么不把标准的try..except
放到函数中呢?@Slayer有趣的是,Python实际上会使用字符串(或任何其他对象)作为或的“替代”对象<代码>0或“不存在”。
将返回“不存在”。
。(我已经测试过了。)@TigerhawkT3我无法访问除以
函数的内部结构-假设它是在一个单独的模块中定义的,我将其用作依赖项。@2Cubed:没有理由感到惊讶<对于x
的所有值,除了0
本身,code>0或x
的计算结果都是x
。有一种方法可以添加类似的内容,但尚未被接受。您有一个很好的建议。我正试图为我的问题创建一个类似的解决方案,但代码无法工作。我已经详细说明了这个问题。如果您能检查这个问题并提供一些建议,我将不胜感激。