Exception mishandling creative solution for What Is Wrong With This Family? by veky - python coding challenges

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Exception mishandling solution in Creative category for What Is Wrong With This Family? by veky

from contextlib import suppress

def is_family(tree):
    with suppress(AssertionError, RecursionError):
        f = {}
        for father, son in tree:
            assert son not in f
            f[son] = father
    
        def oldest_ancestor(person):
            with suppress(KeyError):
                return oldest_ancestor(f[person])
            return person
    
        patriarchs = set(map(oldest_ancestor, f))
        return len(patriarchs) == 1
    
    return False

Oct. 7, 2016

Comments:

veky on Oct. 7, 2016, 8:34 a.m.
I could suppress the StopIteration near the end, but decided this was enough. :-D

Dodge_545c07bd039b4e1aa1a6dd88 on Oct. 8, 2016, 9:30 p.m.
It is more readable to return value than create assert and handle it. <pre class='brush: python'>for father, son in tree: if son in f: return False </pre> If you want to find the patriarchs, just extract all sons from all fathers (patriarchs has no father): <pre class='brush: python'>patriarchs = set(fathers) - set(sons) </pre> P.S. Completely suppresses exceptions is bad practice.

veky on Oct. 9, 2016, 9:22 a.m.
What part of Solution(category=Creative, author=Veky, name='Exception mishandling') did you not understand? :-) Of course this isn't (nor is meant to be) the standard approach. [On the creative hand: didn't you ever want to test whether suppress context manager was re-entrant?;] <hr /> Your other comment is correct - if I only need to find the patriarchs. But I still need oldest_ancestor to detect runaway recursion. So it seemed more straightforward to use it to calculate patriarchs.

DiZ on Oct. 13, 2016, 10:22 a.m.
In his defence, this mission is still in collecting phase, so only random review enabled... So bad! I wanted to see your solution to String conversion, given your comment in its topic, but I wasn't able to find it.

veky on Oct. 13, 2016, 12:45 p.m.
Ah, but still, the category and the name are visible, even in random review, right? Anyway, about String conversion... sorry, but get_opcodes doesn't really give the best match always. They mention it in the docs: <blockquote> This does not yield minimal edit sequences, but does tend to yield matches that “look right” to people. </blockquote> ...so, it's not the right tool there. Too bad.

DiZ on Oct. 13, 2016, 1:21 p.m.
Category is "visible" but picked randomly, and author is only visible after validating your comment. But the worst is that I get a direct link to your answer but can't access it by clicking on it on CheckiO as it fires a random review for all direct links to anyone's solution as long as the mission is in collecting phase. Too bad for `get_opcodes`. Nevermind, I will take a look at your solution when this phase is over! ----- Mail original -----

DiZ on Oct. 13, 2016, 10:15 a.m.
Such exotic lib with use of recent RecursionError, I bet this solution is Veky's! Nice union-find algorithm, although handling cycles by exceeding max depth recursion limit seems a bit inefficient (and wrong on very big graph - 1000 edges, isn't it? - but I don't hope such big tests at CheckIO :-P)

veky on Oct. 13, 2016, 12:27 p.m.
Yes, I thought to use sys.setrecursionlimit, but as you said, it's not clear whether to set it up or down from the default limit (yes, 1000).

suic on March 28, 2017, 1:48 p.m.
Thanks, I didn't know about `contextlib.suppress`. :)

veky on March 28, 2017, 2:08 p.m.
Oh, horrors. :-P How many times did you write <pre class='brush: python'>try: some horribly convoluted code except SomePreciseException: pass </pre> and wanted to put SomePreciseException before the horribly convoluted code, so people know what to expect? :-)

r_tchaik on July 3, 2020, 2:41 a.m.
Very interesting and nice solution. Really creative.

smalcom on Aug. 30, 2023, 6:21 p.m.
Interesting as demonstration for 'contextlib'.

veky on Aug. 31, 2023, 6:28 p.m.
... and as an antidemonstration of assert. :-)

Look up in the Dict()

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