4 ms·

The original code snippet had no bugs until you added more code, stop arguing in bad faith. Also, the new snippet has a syntax error, the last version where th

by doteka 6y ago

The original code snippet had no bugs until you added more code, stop arguing in bad faith. Also, the new snippet has a syntax error, the last version where this was valid reached end of life January 1st, and has been deprecated for 10 years prior to that. Not sure how much stock to put in your python opinions given that context.

mehrdadn 6y ago
> The original code snippet had no bugs until you added more code, stop arguing in bad faith. Wow, that's a really low blow. I'm arguing in perfectly good faith. Failing to call the base class initializer introduces misbehavior in multiple inheritance and the way this happens in Python is completely unexpected. Not every language is like this. > Also, the new snippet has a syntax error, the last version where this was valid reached end of life January 1st, and has been deprecated for 10 years prior to that. Not sure how much stock to put in your python opinions given that context. Er, what syntax error are you talking about? https://ideone.com/3hI4Wj https://ideone.com/3hI4Wj
- WesolyKubeczek 6y ago
  You're still arguing in bad faith. Your original code snippet didn't mention any kind of inheritance at all.
  - deleted 6y ago
    [deleted]
- ZephyrBlu 6y ago
  > Wow, that's a really low blow. I'm arguing in perfectly good faith. Failing to call the base class initializer introduces misbehavior in multiple inheritance and the way this happens in Python is completely unexpected. Not every language is like this Isn't this a bug in class C, not your original snippet? I'm also not sure what you mean by "failing to call the base class initializer introduces misbehavior in multiple inheritance", this seems like an issue related to the MRO of the inherited classes. If you write class C with class B inherited first, the code runs. Example: https://repl.it/repls/BumpyPreemptiveQuerylanguage https://repl.it/repls/BumpyPreemptiveQuerylanguage
  - mehrdadn 6y ago
    > Isn't this a bug in class C, not your original snippet? It's not. The bug is in A.__init__. It needs to call super().__init__(). C would work fine in that case.
    - jbay808 6y ago
      I take it that your claim is that every class should always call super().__init__(), or else it's a bug? What makes you think so?
      - mehrdadn 6y ago
        The answer is a qualified "yes". Because not only can it no longer participate in multiple inheritance, but it is very prone to misbehaving silently when used in such a manner, even for experienced Python users. I say qualified because whether or not the bug warrants fixing is another matter. It's more warranted for public-facing APIs than internal code, since it's less practical for downstream users to modify your code. In your internal code, if your team knows about the issue or just avoids multiple inheritance altogether, or if you have some kind of static analysis to check class hierarchies for you, it might be safe to avoid. (Just listing some considerations that I can think of. There might be more.) My overall point though was just to illustrate one particular example of a flaw that catches even experienced Python developers off-guard, let alone beginners.
        pansa2 6y ago
        > every class should always call super().__init__() For this to work, should every class also have an __init__ method that accepts zero arguments?
        mehrdadn 6y ago
        That's an excellent question and this opens the door to another another interesting discussion. I don't have the energy for that unfortunately, but to reply to your comment: it's not really important that it succeeds per se. Drastically increasing the likelihood of an error is good enough. What's important is that it mitigates the chances of introducing a bug silently.

by doteka 6y ago

mehrdadn 6y ago

> The original code snippet had no bugs until you added more code, stop arguing in bad faith. Wow, that's a really low blow. I'm arguing in perfectly good faith. Failing to call the base class initializer introduces misbehavior in multiple inheritance and the way this happens in Python is completely unexpected. Not every language is like this. > Also, the new snippet has a syntax error, the last version where this was valid reached end of life January 1st, and has been deprecated for 10 years prior to that. Not sure how much stock to put in your python opinions given that context. Er, what syntax error are you talking about? https://ideone.com/3hI4Wj https://ideone.com/3hI4Wj

WesolyKubeczek 6y ago
You're still arguing in bad faith. Your original code snippet didn't mention any kind of inheritance at all.
- deleted 6y ago
  [deleted]
ZephyrBlu 6y ago
> Wow, that's a really low blow. I'm arguing in perfectly good faith. Failing to call the base class initializer introduces misbehavior in multiple inheritance and the way this happens in Python is completely unexpected. Not every language is like this Isn't this a bug in class C, not your original snippet? I'm also not sure what you mean by "failing to call the base class initializer introduces misbehavior in multiple inheritance", this seems like an issue related to the MRO of the inherited classes. If you write class C with class B inherited first, the code runs. Example: https://repl.it/repls/BumpyPreemptiveQuerylanguage https://repl.it/repls/BumpyPreemptiveQuerylanguage
- mehrdadn 6y ago
  > Isn't this a bug in class C, not your original snippet? It's not. The bug is in A.__init__. It needs to call super().__init__(). C would work fine in that case.
  - jbay808 6y ago
    I take it that your claim is that every class should always call super().__init__(), or else it's a bug? What makes you think so?
    - mehrdadn 6y ago
      The answer is a qualified "yes". Because not only can it no longer participate in multiple inheritance, but it is very prone to misbehaving silently when used in such a manner, even for experienced Python users. I say qualified because whether or not the bug warrants fixing is another matter. It's more warranted for public-facing APIs than internal code, since it's less practical for downstream users to modify your code. In your internal code, if your team knows about the issue or just avoids multiple inheritance altogether, or if you have some kind of static analysis to check class hierarchies for you, it might be safe to avoid. (Just listing some considerations that I can think of. There might be more.) My overall point though was just to illustrate one particular example of a flaw that catches even experienced Python developers off-guard, let alone beginners.
      - pansa2 6y ago
        > every class should always call super().__init__() For this to work, should every class also have an __init__ method that accepts zero arguments?
        mehrdadn 6y ago
        That's an excellent question and this opens the door to another another interesting discussion. I don't have the energy for that unfortunately, but to reply to your comment: it's not really important that it succeeds per se. Drastically increasing the likelihood of an error is good enough. What's important is that it mitigates the chances of introducing a bug silently.