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Written by Thomas Arildsen on 2024-08-30 at 11:24

Why can I unpack a #Python set when sets are unordered?

https://stackoverflow.com/q/78931736/865169

[#]computerscience

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Written by gram on 2024-08-30 at 11:36

@arildsen

Because sets are iterable. And they are iterable because you want the "for" loop to work with sets. It's quite often useful to iterate over all the values in set, even if the order is not guaranteed.

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Written by Thomas Arildsen on 2024-08-30 at 12:02

@orsinium I can see how it's useful to be able to iterate them. I guess it means I have to be careful with unpacking them. I find it difficult to imagine a situation where I can use variables unpacked from elements of a set for something 🤔

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Written by gram on 2024-08-30 at 12:05

@arildsen

Unpacking is in general not that often used, TBH. In case of sets, it's one of several ways to get a value from a single-value set and ensure along the way that there is exactly one value:

first, = some_set

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Written by Thomas Arildsen on 2024-08-30 at 12:07

@orsinium I often use unpacking when returning multiple values from a function. But then again, I would never use a set for that.

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Written by gram on 2024-08-30 at 12:10

@arildsen

Returning multiple values from a function is a code smell. I advise people to either split the function in two separate functions or to return a dataclass, giving each return value an explicit name. Depends on cohesion.

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Written by Thomas Arildsen on 2024-08-30 at 21:30

@orsinium hmm, it seems I stand corrected. What if a function's computations of two different things are tightly intertwined and you need both things? Then splitting it into two functions would necessitate repeating much of the functionality in both functions - not really good practice IMO. I guess in that case you would argue for the structured output (dataclass)?

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Written by gram on 2024-08-31 at 04:36

@arildsen

Yes. Or they need to be split on more than 2 functions. I don't think I ever used tuple return in Python in my 10 year career, it's just how my brain works. So, it's certainly possible :)

Interestingly, I use tuples and unpacking all the time in Go, Rust, And Elixir.

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