Python: splitting a string into two parts at the nth delimiter

test-split-tail-head.py

from timeit import timeit
import re

def a(s, delim, n):
    '''
    Two-param split, retaining head
    '''
    r = s.split(delim, n)[n]
    return s[:-len(r)-len(delim)], r

def b(s, delim, n):
    '''
    Iterative find, retaining head
    '''
    index = -1
    while n > 0:
        index = s.find(delim, index+1)
        if index < 0:
            break
        n -= 1
    return s[:index], s[index+1:]

_re_cache1 = dict()
def c(s, c, n):
    '''
    Regular expressions, retaining head
    '''
    r = _re_cache1.get(c, None)
    if r is None:
        _re_cache1[c] = r = re.compile(br'^((?:[^%c]*%c){%d}[^%c]*)%c(.*)' % (c,c,n-1,c,c))
    l = ()
    m = r.match(s)
    if m:
        return m.groups()

def d(s, delim, n):
    '''
    Two-param split, discarding head
    '''
    return s.split(delim, n)[n]

def e(s, delim, n):
    '''
    Iterative find, discarding head
    '''
    index = -1
    while n > 0:
        index = s.find(delim, index+1)
        if index < 0:
            break
        n -= 1
    return s[index+1:]

_re_cache2 = dict()
def f(s, c, n):
    '''
    Regular expressions, discarding head
    '''
    r = _re_cache2.get(c, None)
    if r is None:
        _re_cache2[c] = r = re.compile(br'^((?:[^%c]*%c){%d}[^%c]*)%c(.*)' % (c,c,n-1,c,c))
    l = ()
    m = r.match(s)
    if m:
        return m.groups()[1]


for x in [a,b,c,d,e,f]:
    print(x.__doc__)
    print(x(b"abc:def:efg:hij:klm", b":", 2))
    print(timeit(x.__name__ + '(b"abc:def:efg", b":", 2)', setup='from __main__ import ' + x.__name__, number=10**7))