bpo-42450: Minor updates to the itertools recipes (GH-23555)

Doc/library/itertools.rst

@@ -755,7 +755,7 @@ which incur interpreter overhead.
        "Count how many times the predicate is true"
        return sum(map(pred, iterable))
 
-   def padnone(iterable):
+   def pad_none(iterable):
        """Returns the sequence elements and then returns None indefinitely.
 
        Useful for emulating the behavior of the built-in map() function.
@@ -809,7 +809,7 @@ which incur interpreter overhead.
                nexts = cycle(islice(nexts, num_active))
 
    def partition(pred, iterable):
-       'Use a predicate to partition entries into false entries and true entries'
+       "Use a predicate to partition entries into false entries and true entries"
        # partition(is_odd, range(10)) --> 0 2 4 6 8   and  1 3 5 7 9
        t1, t2 = tee(iterable)
        return filterfalse(pred, t1), filter(pred, t2)
@@ -881,7 +881,7 @@ which incur interpreter overhead.
    def random_product(*args, repeat=1):
        "Random selection from itertools.product(*args, **kwds)"
        pools = [tuple(pool) for pool in args] * repeat
-       return tuple(random.choice(pool) for pool in pools)
+       return tuple(map(random.choice, pools))
 
    def random_permutation(iterable, r=None):
        "Random selection from itertools.permutations(iterable, r)"
@@ -900,11 +900,11 @@ which incur interpreter overhead.
        "Random selection from itertools.combinations_with_replacement(iterable, r)"
        pool = tuple(iterable)
        n = len(pool)
-       indices = sorted(random.randrange(n) for i in range(r))
+       indices = sorted(random.choices(range(n), k=r))
        return tuple(pool[i] for i in indices)
 
    def nth_combination(iterable, r, index):
-       'Equivalent to list(combinations(iterable, r))[index]'
+       "Equivalent to list(combinations(iterable, r))[index]"
        pool = tuple(iterable)
        n = len(pool)
        if r < 0 or r > n:

Lib/test/test_itertools.py

@@ -2290,7 +2290,7 @@ def test_permutations_sizeof(self):
 ...     "Count how many times the predicate is true"
 ...     return sum(map(pred, iterable))
 
->>> def padnone(iterable):
+>>> def pad_none(iterable):
 ...     "Returns the sequence elements and then returns None indefinitely"
 ...     return chain(iterable, repeat(None))
 
@@ -2460,7 +2460,7 @@ def test_permutations_sizeof(self):
 >>> list(pairwise('a'))
 []
 
->>> list(islice(padnone('abc'), 0, 6))
+>>> list(islice(pad_none('abc'), 0, 6))
 ['a', 'b', 'c', None, None, None]
 
 >>> list(ncycles('abc', 3))