[Python-ideas] iter() on steroids

George Sakkis george.sakkis at gmail.com
Fri Apr 13 06:39:41 CEST 2007

I proposed an (admittedly more controversial) version of this a few
months back at the py3k list and the reaction was unexpectedly (IMO)
negative or indifferent, so I'm wondering if things have changed a bit

The proposal is to make the the builtin iter() return an object with
an API that consists of (most) functions currently at itertools. In
addition to saving one "from itertools import chain,islice,..." line
in every other module I write these days, an extra bonus of the OO
interface is that islice can be replaced with slice syntax and chain
with '+' (and/or perhaps the "pipe" character '|'). As a (deliberately
involved) example, consider this:

# A composite iterator over two files specified as follows:
# - each yielded line is right stripped.
# - the first 3 lines of the first file are yielded.
# - the first line of the second file is skipped and its next 4 lines
are yielded
# - empty lines (after the right stripping) are filtered out.
# - the remaining lines are enumerated.

f1,f2 = [iter(open(f)).map(str.rstrip) for f in 'foo.txt','bar.txt']
for i,line in (f1[:3] + f2[1:5]).filter(None).enumerate():
	print i,line

The equivalent itertools version is left as an exercise to the reader.

This is actually backwards compatible and could even go in 2.x if
accepted, but I'm focusing on py3K here.

Comments ?


PS: FYI, a proof of concept implementation is posted as a recipe at:

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