问设计一个能够串行访问多个HTTP请求的系统

EN

def main():
  a = get_a()
  b = get_b(a)

def get_a():
  res = requests.get("https://example.com/a")
  res.raise_for_status()
  data = res.json()
  return data["a"]

def get_b(a):
  res = requests.get("https://example.com/b", params={"a": a})
  res.raise_for_status()
  data = res.json()
  # "y" field is optional
  return data["x"] + data.get("y", 0)

import functools, json, hashlib, glob, os


def clear_cache(stem = "checkpoint"):
  for cache_file in glob.glob(f"{stem}.*.json"):
    os.remove(cache_file)


def sha256_json_fingerprint(data):
  data_as_json = json.dumps(data, sort_keys=True)
  return hashlib.sha256(data_as_json.encode()).hexdigest()


def cached(fn, *, name = ""):
  name = name or fn.__name__

  @functools.wraps(fn)
  def wrapped_fn(*args, **kwargs):
    # assuming all args and kwargs can be converted to JSON
    key = sha256_json_fingerprint([args, kwargs])
    filename = f"checkpoint.{name}.{key}.json"

    # try loading the cached result
    try:
      with open(filename) as f:
        return json.load(f)
    except OsError:
      pass

    # remove outdated files
    clear_cache(f"checkpoint.{name}")

    # fall back to executing the target function
    result = fn(*args, **kwargs)
    with open(filename, "w") as f:
      json.dump(result, f)
    return result

  return wrapped_fn 


@cached
def get_a():
  ...