为什么把 handle 拆出来

真机上的壳（标准库 http.server）：

from http.server import BaseHTTPRequestHandler, HTTPServer


class H(BaseHTTPRequestHandler):
    def _serve(self, method):
        n = int(self.headers.get("Content-Length") or 0)
        body = self.rfile.read(n).decode("utf-8") if n else ""
        status, headers, text = handle(method, self.path, body, NOTES)
        data = text.encode("utf-8")
        self.send_response(status)
        for k, v in headers.items():
            self.send_header(k, v + ("; charset=utf-8" if k == "Content-Type" and v.startswith("text/") else ""))
        self.send_header("Content-Length", str(len(data)))
        self.end_headers()
        if method != "HEAD":
            self.wfile.write(data)

    def do_GET(self):
        self._serve("GET")

    def do_POST(self):
        self._serve("POST")

    def do_HEAD(self):
        self._serve("HEAD")

NOTES = []
HTTPServer(("127.0.0.1", 8000), H).serve_forever()

H 类里几乎没有逻辑，全都转给 handle()。这样拆的最大好处是【0】。