def to_hostlist_fast()

in scripts/util.py [0:0]

• 45 lines of code
• 14 McCabe index (conditional complexity)

def to_hostlist_fast(names: Iterable[str]) -> str:
    """
    Fast implementation of to_hostlist that doesn't invoke `scontrol`
    IMPORTANT:
    * Acts as `scontrol show hostlistsorted`, i.e. original order is not preserved
    * Achieves worse compression than `to_hostlist` for some cases
    """
    pref = defaultdict(list)
    tokenizer = re.compile(r"^(.*?)(\d*)$")
    for name in filter(None, names):
        p, s = tokenizer.match(name).groups()
        pref[p].append(s)

    def _compress_suffixes(ss: List[str]) -> List[str]:
        cur, res = None, []

        def cur_repr():
            nums, strs = cur
            if nums[0] == nums[1]:
                return strs[0]
            return f"{strs[0]}-{strs[1]}"

        for s in sorted(ss, key=int):
            n = int(s)
            if cur is None:
                cur = ((n, n), (s, s))
                continue

            nums, strs = cur
            if n == nums[1] + 1:
                cur = ((nums[0], n), (strs[0], s))
            else:
                res.append(cur_repr())
                cur = ((n, n), (s, s))
        if cur:
            res.append(cur_repr())
        return res

    res = []
    for p in sorted(pref.keys()):
        sl = defaultdict(list)
        for s in pref[p]:
            sl[len(s)].append(s)
        cs = []
        for ln in sorted(sl.keys()):
            if ln == 0:
                res.append(p)
            else:
                cs.extend(_compress_suffixes(sl[ln]))
        if not cs:
            continue
        if len(cs) == 1 and "-" not in cs[0]:
            res.append(f"{p}{cs[0]}")
        else:
            res.append(f"{p}[{','.join(cs)}]")
    return ",".join(res)