[Python-checkins] Add recipe for subslices (GH-31028)

[rhettinger]

https://github.com/python/cpython/commit/06a491179f2de106d34c6b4973a32dce08fc4247
commit: 06a491179f2de106d34c6b4973a32dce08fc4247
branch: main
author: Raymond Hettinger <rhettinger at users.noreply.github.com>
committer: rhettinger <rhettinger at users.noreply.github.com>
date: 2022-02-01T22:18:52-06:00
summary:

Add recipe for subslices (GH-31028)

files:
M Doc/library/itertools.rst

diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index f0d93ebb6b21a..8c3b7842f7f6a 100644
--- a/Doc/library/itertools.rst
+++ b/Doc/library/itertools.rst
@@ -893,6 +893,12 @@ which incur interpreter overhead.
            yield from it
        return true_iterator(), remainder_iterator()
 
+   def subslices(seq):
+       "Return all contiguous non-empty subslices of a sequence"
+       # subslices('ABCD') --> A AB ABC ABCD B BC BCD C CD D
+       slices = starmap(slice, combinations(range(len(seq) + 1), 2))
+       return map(operator.getitem, repeat(seq), slices)
+
    def powerset(iterable):
        "powerset([1,2,3]) --> () (1,) (2,) (3,) (1,2) (1,3) (2,3) (1,2,3)"
        s = list(iterable)
@@ -1188,6 +1194,9 @@ which incur interpreter overhead.
     >>> ''.join(remainder)
     'dEfGhI'
 
+    >>> list(subslices('ABCD'))
+    ['A', 'AB', 'ABC', 'ABCD', 'B', 'BC', 'BCD', 'C', 'CD', 'D']
+
     >>> list(powerset([1,2,3]))
     [(), (1,), (2,), (3,), (1, 2), (1, 3), (2, 3), (1, 2, 3)]