First thing I thought when I saw the title on Reddit was “Oooh, shiny, I like a good rant”

Where’s the rant ?

You cannot rant in less than at least 6 paras (including > 40% ALLCAPs), or 10 paras in lower case.

2 substantial paras abd a few supportings paras does not qualify as a rant.
It’s os merely a whinge.

Bobby:
Of course, and indeed I wrote up a few of those and put them in my standard utilities import, which by now has grown quite a bit. By the way, instead of izip with count, why not just use enumerate?

Dave:
I disagree, although you are partially correct. Indeed when I thought of find and rfind what I had in mind was looking for a single element’s position (a bit like C’s strchr()). Consider:
[python]
def rfind(some_list, criterion, start_pos=None):
if start_pos is None:
start_pos = len(some_list)-1
for idx in range(start_pos, -1, -1):
if criterion(some_list[idx]):
return idx
return None
[/python]

Now, I admit I wanted these functions mostly for some ad-hoc parsing. Still, it would be nice to split a list on token types, or other delimiting objects. for example my_split([1,2,4,0,5,6,7,0,2,5,1], lambda x: x == 0) would return [[1,2,4,],[5,6,7],[2,5,1]].
Regarding regular expressions, again, I wanted this for parsing. This capability is somewhat supported in nltk, where you can define regular expressions for token types for chunks. See section 7.2, subsection “Tag Patterns” in http://nltk.googlecode.com/svn/trunk/doc/book/ch07.html .
I just want a similar capability for lists. (as an aside, regular expression theory allows for any sequence of elements from an alphabet.)

Miki:
Thanks for the link, I wasn’t aware of that.

A String is a sequence of characters while a List is a sequence of objects. The concept of find() assumes a (sub)string comparison. That isn’t possible with a List, which may contain ints, floats, object instances, etc. However, if you know your list is all strings (or sequences)…

def find( alist, pattern):
return [x in alist if pattern in x][0]

def rfind( alist, pattern):
return [x in alist.reverse() if pattern in x][0]

you can replace the if clause with your custom function, as needed.

As for split(), the list is already delimited by it’s elementization, so….I’m not sure what you’re trying to do.

As for regex’s, are you regex’ing across the entire list? If so, do a .join() then apply the regex. If you are appling the regex to the elements in a list, then iterate it and apply the regex.

from itertools import count, ifilter, izip
def list_find(L, func):
for i,d in ifilter(lambda x: func(x[1]), izip(count(), L)):
return i
return -1