https://github.com/python/cpython/commit/b6d8aa436b0108fcc90cb13f9be864cfd4ea2ca7
commit: b6d8aa436b0108fcc90cb13f9be864cfd4ea2ca7
branch: main
author: Raymond Hettinger <[email protected]>
committer: rhettinger <[email protected]>
date: 2026-02-04T14:21:20-06:00
summary:
Itertools recipes: Replace the tabulate() example with running_mean()
(gh-144483)
files:
M Doc/library/itertools.rst
diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index 08dacb505f7748..4f73a74bdd17e2 100644
--- a/Doc/library/itertools.rst
+++ b/Doc/library/itertools.rst
@@ -845,7 +845,8 @@ and :term:`generators <generator>` which incur interpreter
overhead.
from contextlib import suppress
from functools import reduce
from math import comb, isqrt, prod, sumprod
- from operator import getitem, is_not, itemgetter, mul, neg
+ from operator import getitem, is_not, itemgetter, mul, neg, truediv
+
# ==== Basic one liners ====
@@ -858,9 +859,10 @@ and :term:`generators <generator>` which incur interpreter
overhead.
# prepend(1, [2, 3, 4]) → 1 2 3 4
return chain([value], iterable)
- def tabulate(function, start=0):
- "Return function(0), function(1), ..."
- return map(function, count(start))
+ def running_mean(iterable):
+ "Yield the average of all values seen so far."
+ # running_mean([8.5, 9.5, 7.5, 6.5]) -> 8.5 9.0 8.5 8.0
+ return map(truediv, accumulate(iterable), count(1))
def repeatfunc(function, times=None, *args):
"Repeat calls to a function with specified arguments."
@@ -913,6 +915,7 @@ and :term:`generators <generator>` which incur interpreter
overhead.
# all_equal('4٤௪౪໔', key=int) → True
return len(take(2, groupby(iterable, key))) <= 1
+
# ==== Data pipelines ====
def unique_justseen(iterable, key=None):
@@ -1021,6 +1024,7 @@ and :term:`generators <generator>` which incur
interpreter overhead.
while True:
yield function()
+
# ==== Mathematical operations ====
def multinomial(*counts):
@@ -1040,6 +1044,7 @@ and :term:`generators <generator>` which incur
interpreter overhead.
# sum_of_squares([10, 20, 30]) → 1400
return sumprod(*tee(iterable))
+
# ==== Matrix operations ====
def reshape(matrix, columns):
@@ -1058,6 +1063,7 @@ and :term:`generators <generator>` which incur
interpreter overhead.
n = len(m2[0])
return batched(starmap(sumprod, product(m1, transpose(m2))), n)
+
# ==== Polynomial arithmetic ====
def convolve(signal, kernel):
@@ -1114,6 +1120,7 @@ and :term:`generators <generator>` which incur
interpreter overhead.
powers = reversed(range(1, n))
return list(map(mul, coefficients, powers))
+
# ==== Number theory ====
def sieve(n):
@@ -1230,8 +1237,8 @@ and :term:`generators <generator>` which incur
interpreter overhead.
[(0, 'a'), (1, 'b'), (2, 'c')]
- >>> list(islice(tabulate(lambda x: 2*x), 4))
- [0, 2, 4, 6]
+ >>> list(running_mean([8.5, 9.5, 7.5, 6.5]))
+ [8.5, 9.0, 8.5, 8.0]
>>> for _ in loops(5):
@@ -1798,6 +1805,10 @@ and :term:`generators <generator>` which incur
interpreter overhead.
# Old recipes and their tests which are guaranteed to continue to work.
+ def tabulate(function, start=0):
+ "Return function(0), function(1), ..."
+ return map(function, count(start))
+
def old_sumprod_recipe(vec1, vec2):
"Compute a sum of products."
return sum(starmap(operator.mul, zip(vec1, vec2, strict=True)))
@@ -1877,6 +1888,10 @@ and :term:`generators <generator>` which incur
interpreter overhead.
.. doctest::
:hide:
+ >>> list(islice(tabulate(lambda x: 2*x), 4))
+ [0, 2, 4, 6]
+
+
>>> dotproduct([1,2,3], [4,5,6])
32
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