[New-bugs-announce] [issue41120] Possible performance improvement for itertools.product example on Python Docs

[Abbas Taher]

New submission from Abbas Taher <altaher_abbas at yahoo.com>:

In the documentation the following example is given:

def product(*args, repeat=1):
    # product('ABCD', 'xy') --> Ax Ay Bx By Cx Cy Dx Dy
    # product(range(2), repeat=3) --> 000 001 010 011 100 101 110 111
    pools = [tuple(pool) for pool in args] * repeat
    result = [[]]
    for pool in pools:
        result = [x+[y] for x in result for y in pool]
    for prod in result:
        yield tuple(prod)

The proposed enhancement uses a nested generator so no intermediate results are created.

def product2(*args, repeat=1):
    def concat(result, pool):
        yield from (x+[y] for x in result for y in pool)
        
    pools = [tuple(pool) for pool in args] * repeat
    result = [[]]
    for pool in pools:
        result = concat(result, pool)
    for prod in result:
        yield (tuple(prod))

----------
assignee: docs at python
components: Documentation
files: product example.py
messages: 372392
nosy: ataher, docs at python
priority: normal
severity: normal
status: open
title: Possible performance improvement for itertools.product example on Python Docs
type: enhancement
Added file: https://bugs.python.org/file49262/product example.py

_______________________________________
Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue41120>
_______________________________________