fileutils.rotate_file(keep=1) 删除刚刚旋转的文件; keep=N 保留 N-1 代

import os, tempfile
from boltons.fileutils import rotate_file
with tempfile.TemporaryDirectory() as d:
    p = os.path.join(d, "f.txt")
    open(p, "w").write("CRITICAL DATA")
    rotate_file(p, keep=1)
    print(sorted(os.listdir(d)))  # [] — 文件已删除，没有保留任何内容
with tempfile.TemporaryDirectory() as d:
    p = os.path.join(d, "f.txt")
    for i in range(1, 6):
        open(os.path.join(d, f"f.{i}.txt"), "w").write(f"gen {i}")
    open(p, "w").write("current")
    rotate_file(p, keep=5)
    print(sorted(os.listdir(d)))  # ['f.1.txt', 'f.2.txt', 'f.3.txt', 'f.4.txt'] — 要求 5 个文件，保留了 4 个

    fns = [filename] + kept_names
    for orig_name, kept_name in reversed(list(zip(fns, fns[1:]))):  # 行 720-723: f.4 → f.5, …, f → f.1
        if not os.path.exists(orig_name):
            continue
        os.rename(orig_name, kept_name)
    if os.path.exists(kept_names[-1]):  # 行 725-726: 然后 f.5 — 刚写入 — 将被删除
        os.remove(kept_names[-1])