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@gmail.com>

diff --git a/Lib/test/test_doctest.py b/Lib/test/test_doctest.py
index 16196fed39247e3f7a95b4209fe5be04ae4ebfbc..3efe5dafc20ad14da32bbf5be11bc5d461005d44 100644 (file)
--- a/Lib/test/test_doctest.py
+++ b/Lib/test/test_doctest.py
@@ -669,7 +669,7 @@ plain ol' Python and is guaranteed to be available.
     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 @@ plain ol' Python and is guaranteed to be available.
     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 82ca317c7e9c265375cca87f623bac3788faec37..199b09c4d8c41e61fda2938c81733eb3859a35c2 100644 (file)
--- 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)