What is the pythonic way to execute multiple conditions, one after the other, while showing to the user which is the first to fail

Question

Let's say I have this working code:

def check_some_conds(args):
    assert (condA(args) or
            condB(args))

    assert condC(args)
    assert condD(args)

    return True

(Yeah, I know that asserts are bad, but please bear with me for a moment)

Now, when I'm calling this function, I can (more or less), retrive the first failed assertion by using a except AssertionError:, and by doing some magic with the traceback module.

However, this is not ideal because:

• assert is optimised-out in python
• I can't really specify an error message
• Playing with the traceback module feels hacky at best
• I still need to get a boolean return value, so catching that and then changing the return value is boilerplate code.

I'm looking for a way to:

• Run multiple conditions, mostly independant one of the other
  • Knowing that some of the functions may be long and must be tried last (here, condD may take seconds
  • And some of them may be async functions or just inline evaluations (a == b)
• return a boolean (optional)
• log a message that says condD failed or nor condA or condB succeded

If that's not really possible, please feel free to suggest partial answers to my problem

Answer 1

Loop through your conditions and raise errors at the end:

fail = False
for condition in [cond1, cond2, cond3 ...]:

    if not condition(args):
        print(condition.__name__, "failed")
        fail = True
    else:
        print(condition.__name__, "succeeded")
if fail: raise ...