Using try/except for conditional logic gives the developer a spurious choice between two different syntaxes to express the same thing. The reader is then asked to read try/except blocks as meaning two different things: either ordinary expected branching in the function, or handling exceptions.

I think it's definitely better if we just use conditionals to express conditionals, and try/except for errors, like every other language does. Here's some examples of where this duplication of syntax causes problems.

* Exceptions are often not designed to match the interface well enough to make this convenient. For instance, 'x in y' works for both mapping types and lists, but only mapping types will raise a `KeyError`. If your function is expected to take any iterable, the correct catching code will be `except (KeyError, IndexError)`. There's all sorts of these opportunities to be wrong. When people write exceptions, they want to make them specific, and they're not necessarily thinking about them as an interface to conveniently check preconditions.

* Exceptions are not a type-checked part of the interface. If you catch `(KeyError, IndexError)` for a variable that's just a dictionary, no type checker (or even linter?) is going to tell you that the `IndexError` is impossible, and you only need to catch `KeyError`. Similarly, if you catch the wrong error, or your class raises an error that doesn't inherit from the class that your calling code expects it to, you won't get any type errors or other linting. It's totally on you to maintain this.

* Exceptions are often poorly documented, and change more frequently than other parts of the interface. A third-party library won't necessarily consider it a breaking change to raise an error on a new condition with an existing error type, but if you're conditioning on that error in a try/except, this could be a breaking change for you.

* The base exceptions are very general, and catching them in code that should be a conditional runs a significant risk of catching an error by mistake. Consider code like this:

    try:
        value = my_dict[some_function()]
    except KeyError:
        ...

Because you must never ever ever call a function inside your conditional try block, you're using a syntax that doesn't compose properly with the rest of the language. So you can either rewrite it to something like this:

    value = some_function()
    try:
        return my_dict[value]
    except KeyError:
        ...

The fundamental thing here is that 'try/except' is a "come from": whether you enter the 'except' block depends on which situations the function (or, gulp, functions) you're calling raise that error. The decision isn't local to the code you're looking at. In contrast, if you write a conditional, you have some local value and you're going to branch based on its truthiness or some property of it. We should only be using the 'try/except' mechanism when we _need_ its vagueness --- when we need to say "I don't know or can't check exactly what could lead to this". If we have a choice to tighten the control flow of the program we should.

And what do you buy for all this spurious decision making and the very high risk of very serious bugs anyway? Why should Python do this differently from every other language? I don't see any benefits in that article linked, and I've never seen any in other discussions of this topic.