gh-131885: update documented signatures for csv.{writer,reader}

[adamtheturtle]

…ter` have some positional-only arguments

importcsvwithopen("example.csv", "w", newline='') ascsvfile:
csv.writer(csvfile=csvfile) # TypeError: expected at least 1 argument, got 0

importcsvcsv.reader(csvfile="a") # TypeError: expected at least 1 argument, got 0

• Issue: Update function signatures to use * and / as needed #131885

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📚 Documentation preview 📚: https://cpython-previews--136085.org.readthedocs.build/

[ZeroIntensity]

LGTM.

Reading the source, I was a little confused at first:

cpython/Modules/_csv.c

Lines 1090 to 1100 in bd928a3

	if (!PyArg_UnpackTuple(args, "reader", 1, 2, &iterator, &dialect)) {
	Py_DECREF(self);
	returnNULL;
	}
	self->input_iter=PyObject_GetIter(iterator);
	if (self->input_iter==NULL) {
	Py_DECREF(self);
	returnNULL;
	}
	self->dialect= (DialectObj*)_call_dialect(module_state, dialect,
	keyword_args);

PyArg_UnpackTuple unpacks positional arguments, so I would have thought that csv.writer(file, dialect="...") wouldn't work, but the catch is that _call_dialect checks if the dialect was non-NULL, and extracts it from the keywords if it is. But, there's nothing similar for csvfile, so this is the correct description for the docs.

[miss-islington-app]

Thanks @adamtheturtle for the PR, and @ZeroIntensity for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

[bedevere-app]

GH-136120 is a backport of this pull request to the 3.14 branch.

[bedevere-app]

GH-136121 is a backport of this pull request to the 3.13 branch.

[ZeroIntensity]

Thanks!