mirrors/cpython
1
0
Fork 0
mirror of https://github.com/python/cpython.git synced 2025-09-30 20:31:52 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 11

Misc Itertools recipe tweaks (GH-100493)

Browse source
This commit is contained in:
Raymond Hettinger 2022-12-24 00:21:30 -08:00 • committed by GitHub
parent 2eea9598e3
commit 0769f95751
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
1 changed files with 49 additions and 5 deletions
Download patch file Download diff file Expand all files Collapse all files

54
Doc/library/itertools.rst
View file

@ -788,6 +788,11 @@ which incur interpreter overhead.
.. testcode:: .. testcode::
import collections
import math
import operator
import random
def take(n, iterable): def take(n, iterable):
"Return first n items of the iterable as a list" "Return first n items of the iterable as a list"
return list(islice(iterable, n)) return list(islice(iterable, n))
@ -892,6 +897,21 @@ which incur interpreter overhead.
data[2] = 1 data[2] = 1
return iter_index(data, 1) if n > 2 else iter([]) return iter_index(data, 1) if n > 2 else iter([])
def factor(n):
"Prime factors of n."
# factor(97) --> 97
# factor(98) --> 2 7 7
# factor(99) --> 3 3 11
for prime in sieve(n+1):
while True:
quotient, remainder = divmod(n, prime)
if remainder:
break
yield prime
n = quotient
if n == 1:
return
def flatten(list_of_lists): def flatten(list_of_lists):
"Flatten one level of nesting" "Flatten one level of nesting"
return chain.from_iterable(list_of_lists) return chain.from_iterable(list_of_lists)
@ -1134,11 +1154,6 @@ which incur interpreter overhead.
Now, we test all of the itertool recipes Now, we test all of the itertool recipes
>>> import operator
>>> import collections
>>> import math
>>> import random
>>> take(10, count()) >>> take(10, count())
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9] [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
@ -1251,6 +1266,35 @@ which incur interpreter overhead.
>>> set(sieve(10_000)).isdisjoint(carmichael) >>> set(sieve(10_000)).isdisjoint(carmichael)
True True
list(factor(0))
[]
list(factor(1))
[]
list(factor(2))
[2]
list(factor(3))
[3]
list(factor(4))
[2, 2]
list(factor(5))
[5]
list(factor(6))
[2, 3]
list(factor(7))
[7]
list(factor(8))
[2, 2, 2]
list(factor(9))
[3, 3]
list(factor(10))
[2, 5]
all(math.prod(factor(n)) == n for n in range(1, 1000))
True
all(set(factor(n)) <= set(sieve(n+1)) for n in range(1, 1000))
True
all(list(factor(n)) == sorted(factor(n)) for n in range(1, 1000))
True
>>> list(flatten([('a', 'b'), (), ('c', 'd', 'e'), ('f',), ('g', 'h', 'i')])) >>> list(flatten([('a', 'b'), (), ('c', 'd', 'e'), ('f',), ('g', 'h', 'i')]))
['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i'] ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i']