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0 pointstyingq4y ago0 comments

>Python is really consistent when it comes to its behaviour

True, though you end up with things like:

  ' '.join(thelist)

Instead of

  thelist.join(' ')

Because of the somewhat aggressive mantra to be consistent.

0 comments

11 comments · 4 top-level

Marazan4y ago· 6 in thread

But that's good. Because a string just needs to know aboit interable to perform that operation whereas every iterable would need to implement it's own join if you had it the other way around.

Someone4y ago

It may be necessary in python, but in general, a language could allow you to define a join method on the iterable superclasss/trait/interface that iterates over the elements, converting each to a string, and inserting the separator between each of them.

For example, scala has Iterable#mkstring (https://docs.scala-lang.org/overviews/collections-2.13/trait...)

goatlover4y ago

Yet Ruby and JS manage to do it somehow. To me it seems natural that join should be a method on the iterable, and I always have to pause to remember Python is different.

aidos4y ago

How does that work? Don’t you have to effectively convert your general iterable to an array and then join on that? Array.from(iterable).join(…)?

globular-toast4y ago

I don't think it should be a method at all. It's just a function: join(iterable, separator). It can also be implemented with reduce naturally: `reduce(lambda x, y: x + separator + y, iterable)`.

1 more reply

ptx4y ago

The way it's managed in JS, digging the function out of the prototype to apply it, can be done in Python as well. But unlike JS you won't normally have to, thanks to the method not being defined only on one specific type of iterable.

JS:

  Array.prototype.join.call(["one", "two", "three"], "|")

Python:

  str.join("|", ["one", "two", "three"])

dragonwriter4y ago

> Yet Ruby and JS manage to do it somehow.

Ruby does it by having a mixin (Enumerable) that anything meeting a basic contract (roughly equivalent to the Python iterable protocol) can include to get an enormous block of functionality; Python doesn’t have (or at least idiomatically use as freely; ISTR that there is a way to do it) mixins like Ruby does.

rndgermandude4y ago· 1 in thread

' '.join() makes more sense to me, and it's more universal too if done right and you accept anything resembling a "sequence" (which python does) and individual objects of the sequence have a sensible str(). And as language maintainer, you only have to maintain one such implementation, not one per collection type.

Javascript, on the other hand, kinda does it worst, at least of the languages I regularly use... .join() is a instance method on Arrays and TypesArrays. But they forgot to add any kind of join for Sets, for example.

    (["a", "b", "c"]).join("")
    "abc" # alright
    (new Set(["a", "b", "c"])).join("")
    Uncaught TypeError: (intermediate value).join is not a function
    ([...new Set(["a", "b", "c"])]).join("")
    "abc" # grmpf, have to materialize it into an array first.

That illustrates the drawback: if you make it a method on the concrete sequence types you got, you better not forget some and make sure the different APIs are consistent, too. If Javascript had a String.join(sep, <anything implementing the iterator protocol>) this wouldn't have been an issue.

python isn't alone either, by the way. C# has the static string.Join(...) that accepts "enumerables" (IEnumerable<T>), but no array.Join() or list.Join() or dictionary.Join(). Combined with Linq, especially .Select, that becomes quite handy. It has been plenty of times I did print-debugging by adding a one liner along the lines of

    Console.WriteLine(string.Join("\n", dictionary.Select((key, value) => $"{key} = {value.SomeProperty}")));

I find the C# way of having a string.Join(sep, ...) instead of python's "some string".join(...) nicer to read because it's more obvious.

pansa24y ago

> I find the C# way of having a string.Join(sep, ...) instead of python's "some string".join(...) nicer to read because it's more obvious.

`str.join(sep, ...)` works in Python as well, because `a.f(...)` and `type(a).f(a, ...)` are (almost) equivalent.

robluxus4y ago

It's more about flexibility than consistency.

str.join() and bytes.join() can support all iterable type arguments.

Better than trying to implement a join (or two) on all iterables.

pdonis4y ago

In the cases you give, the original list is not being mutated; a new object (a string, not a list) is being created. So it does make sense not to have it be a method call on the list.

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