从零开始写博客系统——数据持久化（文件）

# article.py

class FileCache(object):
    def __init__(self) -> None:
        self._md5 = ""
        self._data = []
        self._filename = "article_cache"
        self._load_cache()

    def _file_exist(self):
        return os.path.exists(self._filename)

    def _load_cache(self):
        if self._file_exist():
            # 从文件中读取数据
            with open(self._filename, "r") as f:
                info = f.read()
                _md5 = info.split("\n")[0]
                _data = json.loads(info.split("\n")[1])
                if self._check_md5(_md5, _data):
                    self._data = _data
                    self._md5 = _md5
        else:
            # 从data中读取数据
            for x in data.article_list:
                at = Article(
                    x.get("id"),
                    x.get("title"),
                    x.get("content"),
                    x.get("author"),
                    x.get("created_time"),
                    x.get("modified_time"),
                    x.get("category"),
                    x.get("tag")
                )
                self._data.append(at.to_dict())
            self._dump_cache()

    def _dump_cache(self):
        self._calc_md5()
        with open(self._filename, "w") as f:
            f.write(self._md5 + "\n" + json.dumps(self._data))

    def _calc_md5(self):
        md5hash = hashlib.md5(json.dumps(self._data).encode("utf-8"))
        self._md5 = md5hash.hexdigest()

    def _check_md5(self, md5info, data):
        md5hash = hashlib.md5(json.dumps(data).encode("utf-8"))
        return md5hash.hexdigest() == md5info

    def to_json(self):
        return {
            "total": self.total,
            "articles": self.articles
        }

    def append(self, article: Article):
        self._data.append(article.to_dict())
        self._dump_cache()

    def get_by_id(self, id: int) -> Article:
        for x in self._data:
            if x.get("id") == id:
                return Article(**x)

    def update_by_id(self, id: int, article: Article) -> bool:
        for i, x in enumerate(self._data):
            if x.get("id") == id:
                self._data[i] = article.to_dict()
                self._dump_cache()
                return True
        return False

    def get_categorys(self) -> list:
        categorys = []
        for x in self._data:
            if x.get("category") not in categorys:
                categorys.append(x.get("category"))
        return categorys

    def get_tags(self) -> list:
        tags = []
        for x in self._data:
            for tag in x.get("tag"):
                if tag not in tags:
                    tags.append(tag)
        return tags

    @property
    def total(self):
        return len(self._data)

    @property
    def articles(self):
        return self._data

# app.py

articles = article.FileCache()