It's a convention, quite a nice one, but not all libraries are consistent and it does have different meanings too (! is sometimes used for "raise an error instead of returning a boolean").
In the Python case, `list.sort()` operates on the object, so you can kind of expect it to do mutation (but there's no convention / guarantee). Though it only makes sense as a function that the list object itself implements.
`sorted` is a general function that gives you a sorted list from any iterable, and because working with iterables is such a common thing in software, Python has a bunch of standard functions like that. It's nice because you learn them once and they apply absolutely everywhere.
Ultimately you learn the behaviours of a language and they become second nature. I find both Ruby and Python very clean and easy to read.
You take out the chars from the string, sort them and then join them together again
because a string cannot be sorted, sorting a string makes no sense, you sort the chars composing it.
Also, Python could not do this for many years, while Ruby could no prob
sorted("gheliabciouß⌚⌨⌛🆔🉑🈶🈚🈸🈺🈷🆚🉐㊙㊗🈴")
edit: Python also shows some very counterintuitive semantic
take the example above, to return a string you use
''.join(sorted("gheliabciou"))
'abceghiilouß'
which is probably the last thing someone would think of.
sorting a list does not produce any output, because sort is _always_ in place, so you have to waste a variable to sort a list because you can't sort it inline
list("fedcba")
['f', 'e', 'd', 'c', 'b', 'a']
print(list("fedcba").sort())
None # <-- where did the list go?
# you have to do
l = list("fedcba")
l.sort()
print(l)
['a', 'b', 'c', 'd', 'e', 'f']
again, highly unexpected
my favourite
print([c for c in "bca"].sort())
None # <- WTF? list comprehension is a functional concept!
# this is how you "intuitively" do it
print(''.join(sorted([c for c in "cba"])))
abc
Lots of objects don't have a natural way to return a sorted version of themselves, especially inplace (what's the reverse sort of a range, for example). You get the same in Ruby, as you've just demonstrated. Sorting into a list is the only thing that makes sense in all cases.
In that way `sorted` _is_ totally consistent - it always takes an iterable and returns a list of the elements. If we can't agree on that then I don't think there's much of a discussion to be had here.
> In that way `sorted` _is_ totally consistent - it always takes an iterable and returns a list of the elements
except Iterable is the wrong "interface"
in Python it is defined as
> An iterable is any Python object capable of returning its members one at a time, permitting it to be iterated over in a for-loop.
which is not always what you want for sorting
quicksort doesn't work one element at a time
so basically you have to extract all the elements before sorting them
what about infinite streams?
At least Ruby Enumerable mixins explicitly states that
> The Enumerable mixin provides collection classes with several traversal and searching methods, and with the ability to __sort__.
Another problem with sorted is that it accepts any iterable, true, returning a list of items, but it is not clear how you can tell if the object is an iterbale or not
>>> sorted(123)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'int' object is not iterable
ok
>>> isinstance(123, iterable)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'iterable' is not defined
mmmm
maybe it's because int is not iterable?
>>> isinstace("abc", iterable)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'iterable' is not defined
so the solutions are
# fails for strings in Python 2
>>> try:
_ = iter(some_object)
except TypeError as te:
print('is not iterable')
or
# if 2.6 >= Python < 3.3
from collections import Iterable
# if Python >= 3.3
from collections.abc import Iterable # <- personal note, abc stands for...? core maybe?
# no idea on how to do it in Python < 2.6
>>> isinstance("abc", Iterable)
True
not only it's very ugly, but it can also fail in mysterious ways. As per documentation
Checking isinstance(obj, Iterable) detects classes that are registered as Iterable or that have an __iter__() method, but it does not detect classes that iterate with the __getitem__() method. The only reliable way to determine whether an object is iterable is to call iter(obj).
In the Python case, `list.sort()` operates on the object, so you can kind of expect it to do mutation (but there's no convention / guarantee). Though it only makes sense as a function that the list object itself implements.
`sorted` is a general function that gives you a sorted list from any iterable, and because working with iterables is such a common thing in software, Python has a bunch of standard functions like that. It's nice because you learn them once and they apply absolutely everywhere.
Ultimately you learn the behaviours of a language and they become second nature. I find both Ruby and Python very clean and easy to read.