One-line Exception Handling

In Python, it is possible to use one-liners to set values with special conditions (such as defaults or conditions) in a simple, intuitive way. result = 0 or 'Does not exist.' # 'D

Solution 1:

It is not possible to do a one-line exception-handling statement in python. One could write a function to do this.

def safe_execute(default, exception, function, *args):
    try:
        returnfunction(*args)
    except exception:
        returndefault

Example usage:

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

Multiple arguments are supported

fromoperator 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.

The error-catching process may still be interrupted:

from time import sleep
safe_execute(
    "Panic!",
    Exception,
    sleep, 8
)
# Ctrl-c will raise a KeyboardInterruptfrom sys import exit
safe_execute("Failed to exit!", Exception, exit)
# Exits the Python interpreter

If this behavior is undesired, use 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!"

Solution 2:

It is possible in one line using exec:

parse_float = lambda x, y=exec("def f(s):\n try:\n  return float(s)\n except:  return None"): f(x)

Solution 3:

You can use contextlib to suppress exceptions. If you like to live dangerously you could suppress BaseException, which would suppress all builtin exceptions (probably a bad idea). Or you could pick a safe one relevant to your code, like TypeError.

examples:

from contextlib import suppress

# this will execute right alongwith suppress(BaseException): fhasldjkfhsa345315

# even raising an Exception will fly just finewith suppress(BaseException): raise NameError

# correct code will execute just fine
x=5with suppress(BaseException): x+=2print(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