Architecture Patterns with Python

Post by maleldil » Mon, Mar 31, 2025, 4:02 PM UTC

pansa2 wrote: post #137

_dain_ wrote: post #135

Earlier quoted context omitted.

Don't do this stupid party trick with `global`. You may as well argue that unit tests are pointless because you could cheat by making the implementations return just the hardcoded values from the test cases.

This isn't a "party trick" with `global`, it's a fundamental hole in the type system: class C: def __init__(self) -> None: self.i : int | list[int] = 0 def foo(self) -> None: self.i = [] def bar(self) -> int: if isinstance(self.i, int): self.foo() return self.i return 0 print(type(C().bar()))

    class C {
        i: number | number[];

        constructor() {
            this.i = 0;
        }

        foo(): void {
            this.i = [];
        }

        bar(): number {
            if (typeof this.i === 'number') {
                this.foo();
                return this.i;
            }
            return 0;
        }
    }

    console.log(typeof new C().bar());

Post by maleldil » Thu, Apr 03, 2025, 1:39 PM UTC

__MatrixMan__ wrote: post #142

maleldil wrote: post #141

Earlier quoted context omitted.

This seems to work in TypeScript too: class C { i: number | number[]; constructor() { this.i = 0; } foo(): void { this.i = []; } bar(): number { if (typeof this.i === 'number') { this.foo(); return this.i; } return 0; } } console.log(typeof new C().bar()); It seems to be a problem with "naked" type unions in general. It's unfortunate.

Agreed, but I've never found it to be especially problematic. The type checker still catches the vast majority of things you'd expect a type checker to catch. If you want to be able to change the type of something at runtime, static analysis isn't always going to be able to have your back 100% of the time. Turns out that's a tradeoff that many are willing to make.