bpo-40636: Clarify the zip built-in docstring. (GH-20118)

gpshead · brandtbucher · web-flow · commit 6a5d3ff67644 · 2020-05-15T14:26:00.000-07:00
Clarify the zip built-in docstring. This puts much simpler text up front along with an example. As it was, the zip built-in docstring was technically correct. But too technical for the reader who shouldn't _need_ to know about `__next__` and `StopIteration` as most people do not need to understand the internal implementation details of the iterator protocol in their daily life. This is a documentation only change, intended to be backported to 3.8; it is only tangentially related to PEP-618 which might offer new behavior options in the future. Wording based a bit more on enumerate per Brandt's suggestion. This gets rid of the legacy wording paragraph which seems too tied to implementation details of the iterator protocol which isn't relevant here. Co-authored-by: Brandt Bucher <brandtbucher@gmail.com>
diff --git a/Lib/test/test_doctest.py b/Lib/test/test_doctest.py
@@ -669,7 +669,7 @@ def non_Python_modules(): r"""
     True
     >>> real_tests = [t for t in tests if len(t.examples) > 0]
     >>> len(real_tests) # objects that actually have doctests
-    12
+    13
     >>> for t in real_tests:
     ...     print('{}  {}'.format(len(t.examples), t.name))
     ...
@@ -685,6 +685,7 @@ def non_Python_modules(): r"""
     2  builtins.int.bit_length
     5  builtins.memoryview.hex
     1  builtins.oct
+    1  builtins.zip
 
 Note here that 'bin', 'oct', and 'hex' are functions; 'float.as_integer_ratio',
 'float.hex', and 'int.bit_length' are methods; 'float.fromhex' is a classmethod,
diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
@@ -2649,12 +2649,15 @@ static PyMethodDef zip_methods[] = {
 };
 
 PyDoc_STRVAR(zip_doc,
-"zip(*iterables) --> zip object\n\
+"zip(*iterables) --> A zip object yielding tuples until an input is exhausted.\n\
 \n\
-Return a zip object whose .__next__() method returns a tuple where\n\
-the i-th element comes from the i-th iterable argument.  The .__next__()\n\
-method continues until the shortest iterable in the argument sequence\n\
-is exhausted and then it raises StopIteration.");
+   >>> list(zip('abcdefg', range(3), range(4)))\n\
+   [('a', 0, 0), ('b', 1, 1), ('c', 2, 2)]\n\
+\n\
+The zip object yields n-length tuples, where n is the number of iterables\n\
+passed as positional arguments to zip().  The i-th element in every tuple\n\
+comes from the i-th iterable argument to zip().  This continues until the\n\
+shortest argument is exhausted.");
 
 PyTypeObject PyZip_Type = {
     PyVarObject_HEAD_INIT(&PyType_Type, 0)
