[Python-checkins] bpo-40636: Clarify the zip built-in docstring. (GH-20118)

[Gregory P. Smith]

https://github.com/python/cpython/commit/6a5d3ff67644af42b1a781be2eacb2e82913441c
commit: 6a5d3ff67644af42b1a781be2eacb2e82913441c
branch: master
author: Gregory P. Smith <greg at krypto.org>
committer: GitHub <noreply at github.com>
date: 2020-05-15T14:26:00-07:00
summary:

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

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 at gmail.com>

files:
M Lib/test/test_doctest.py
M Python/bltinmodule.c

diff --git a/Lib/test/test_doctest.py b/Lib/test/test_doctest.py
index 16196fed39247..3efe5dafc20ad 100644
--- 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
index 82ca317c7e9c2..199b09c4d8c41 100644
--- 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)