1.安装
1.1 创建虚拟环境
mkdir myproject cd myproject python3 -m venv venv
1.2 进入虚拟环境
. venv/bin/activate
1.3 安装 flask
pip install flask
2.上手
2.1 最小 demo
将下列代码保存为 hello.py
:
from flask import flask app = flask(__name__) @app.route("/") def hello_world(): return "<p>hello, world!</p>"
运行上述代码:
export flask_app=hello flask run
这样访问:http://127.0.0.1:5000 会看到 hello, world!
2.2 基本知识
这里有 flask 的基本知识(非常重要的基础,大家可以自己看:链接
1.html escaping (利用 jinja,参考:
2.routing (下面几个例子)
@app.route('/') def index(): return 'index page' @app.route('/hello') def hello(): return 'hello, world' @app.route('/user/<username>') def show_user_profile(username): # show the user profile for that user return f'user {escape(username)}' @app.route('/post/<int:post_id>') def show_post(post_id): # show the post with the given id, the id is an integer return f'post {post_id}' @app.route('/path/<path:subpath>') def show_subpath(subpath): # show the subpath after /path/ return f'subpath {escape(subpath)}'
3.http methods
@app.route('/login', methods=['get', 'post']) def login(): if request.method == 'post': else:
4.static files (url_for('static', filename='style.css')
)
5.rendering templates (这个参考之前的 jinja)
6.file uploads、cookies、redirects and errors、about responses、apis with json、sessions、message flashing、logging 这些等我们实际用到时再过来看
3.解构官网指导 demo
第 1 节教大家如何利用 python 虚拟环境,快速构建 flask 环境;第 2 节带着大家简单熟悉了 flask 的编程规则(或风格)。
大家在着手本节时,务必将第 2 节中的基础的代码跟着官网敲一下!因为,这一节我们不是由简到难一步步搭建 flask 服务器,而是直接拿搭建好的反过来分析。
3.1 克隆与代码架构分析
$ git clone https://github.com/pallets/flask $ cd flask $ cd examples/tutorial
代码目录结构如下:
3.2 入口文件 init.py
def create_app(test_config=none): """create and configure an instance of the flask application.""" # 1-创建一个 flask 实例 # 并设置一些 app 需要用到的参数 app = flask(__name__, instance_relative_config=true) app.config.from_mapping( # a default secret that should be overridden by instance config secret_key="dev", # store the database in the instance folder database=os.path.join(app.instance_path, "flaskr.sqlite"), ) # 2-测试用的 if test_config is none: # load the instance config, if it exists, when not testing app.config.from_pyfile("config.py", silent=true) else: # load the test config if passed in app.config.update(test_config) # 3-创建一个文件夹,用来存 db 运行时的产生的文件 # ensure the instance folder exists try: os.makedirs(app.instance_path) except oserror: pass @app.route("/hello") def hello(): return "hello, world!" # register the database commands # 3.3 数据库设置(为 flask 新增一个 init_db 命令,这样直接敲 flask init_db 就能生成表) from flaskr import db db.init_app(app) # apply the blueprints to the app # #### 3.4 蓝图和视图(基于蓝图来管理组织视图,视图注册到蓝图,蓝图注册到应用) from flaskr import auth, blog app.register_blueprint(auth.bp) app.register_blueprint(blog.bp) # make url_for('index') == url_for('blog.index') # in another app, you might define a separate main index here with # app.route, while giving the blog blueprint a url_prefix, but for # the tutorial the blog will be the main index app.add_url_rule("/", endpoint="index") return app
3.3 数据库设置
该项目采用了 sqlite 作为数据库(python 内置了,免去安装和配置工作)。
1.sql 文件 schema.sql
sqlite 的数据存储在表格中,在向表格增删改查数据前,需要先建表。该项目中的 schema.sql 编写了建表的 sql 语句。分别创建了一个 user 表和 post 表。
drop table if exists user; drop table if exists post; create table user ( id integer primary key autoincrement, username text unique not null, password text not null ); create table post ( id integer primary key autoincrement, author_id integer not null, created timestamp not null default current_timestamp, title text not null, body text not null, foreign key (author_id) references user (id) );
2)与数据库建立连接与断开
def get_db(): """connect to the application's configured database. the connection is unique for each request and will be reused if this is called again. """ if "db" not in g: g.db = sqlite3.connect( current_app.config["database"], detect_types=sqlite3.parse_decltypes ) g.db.row_factory = sqlite3.row return g.db def close_db(e=none): """if this request connected to the database, close the connection. """ db = g.pop("db", none) if db is not none: db.close()
g 是一个特殊结构,对于每次请求,会产生一个。
3)数据库初始化(生成表)
第 1 节的 schema.sql 用于建表,那么如何执行其中的建表命令呢? db.py 中的 init_db 就是干这个事情的。
def init_db(): """clear existing data and create new tables.""" db = get_db() # 获取数据库(如果没有则创建) # 读取 schema.sql 中的 sql 命令,并用 db.executescript 执行 sql 命令 with current_app.open_resource("schema.sql") as f: db.executescript(f.read().decode("utf8"))
4)将 init_db 注册为 flask 命令
由于数据库初始化并不需要每次启动数据库时运行(不属于运行时需要执行的函数),我们需要将注册成 flask 一个指令,只要在命令行中敲 flask init-db
就能够执行 init_db
,其实现方法如下:
@click.command("init-db") @with_appcontext def init_db_command(): """clear existing data and create new tables.""" init_db() click.echo("initialized the database.") def init_app(app): """register database functions with the flask app. this is called by the application factory. """ app.teardown_appcontext(close_db) # 在返回响应后进行清理时调用该函数 app.cli.add_command(init_db_command) # 添加一个可以用flask命令调用的新命令
这样,执行完之后,flask.sqlite 文件将会出现在 instance 文件夹。
3.4 蓝图和视图
蓝图是一种组织一组相关视图和其他代码的方法。它们不是直接向应用程序注册视图和其他代码,而是向蓝图注册。然后,当蓝图在factory函数中可用时,它将在应用程序中注册。
该项目中有两个蓝图:auth 和 blog
bp = blueprint("auth", __name__, url_prefix="/auth") # in auth.py bp = blueprint("blog", __name__) # in blog.py
参数分别是:蓝图的名字,import_name(一般为 __name__),url 前缀
[1].官方 demo github 仓库
1)auth 视图
这里主要有三个路由:
@bp.route("/register", methods=("get", "post")) def register(): ... @bp.route("/login", methods=("get", "post")) def login(): ... @bp.route("/logout") def logout():
2)blog 视图
这里主要有四个路由:
@bp.route("/") def index(): ... @bp.route("/create", methods=("get", "post")) @login_required def create(): ... @bp.route("/<int:id>/update", methods=("get", "post")) @login_required def update(id): ... @bp.route("/<int:id>/delete", methods=("post",)) @login_required def delete(id): ...
3)注册视图中各个功能实现介绍
注册
注册逻辑为:首先从 post 中获取 username 和 password,然后调用数据库插入操作:
username = request.form["username"]
password = request.form["password"]
db.execute("insert into user (username, password) values (?, ?)", (username, generate_password_hash(password)),)
登录
登录逻辑为:首先从 post 中获取 username 和 password,然后调用数据库查询操作,获取该用户的密码,然后进行密码匹配:
user = db.execute("select * from user where username = ?",username,)).fetchone()
check_password_hash(user["password"], password)
密码匹配后,需要创建 session:
if error is none: # store the user id in a new session and return to the index session.clear() session["user_id"] = user["id"] return redirect(url_for("index"))
注销
注销需要清空 session:
session.clear()
session
session 逻辑如下:注册一个方法,让其在任何 url 请求之前执行,在其中做 session 管理:
@bp.before_app_request def load_logged_in_user(): user_id = session.get('user_id') if user_id is none: g.user = none else: g.user = get_db().execute( 'select * from user where id = ?', (user_id,) ).fetchone()
其他 view 使用认证
其他 view 也想使用认证该如何做?在 auth.py 中实现 login_required 函数,判断 user 是否为空,如果为空,则跳转到登录页面:
def login_required(view): @functools.wraps(view) def wrapped_view(**kwargs): if g.user is none: return redirect(url_for('auth.login')) return view(**kwargs) return wrapped_view
4)博客视图中各个功能实现介绍
展示所有博客
逻辑如下:执行数据库查询操作,获取所有博客,然后加载:
@bp.route("/") def index(): """show all the posts, most recent first.""" db = get_db() posts = db.execute( "select p.id, title, body, created, author_id, username" " from post p join user u on p.author_id = u.id" " order by created desc" ).fetchall() return render_template("blog/index.html", posts=posts)
创建博客
逻辑如下:函数前加上 @login_required
前缀,这样就能自动判断是否已经登录,否则跳到登录页面;创建博客就是获取标题和内容,然后调用插入命令,进行插入:
@bp.route("/create", methods=("get", "post")) @login_required def create(): """create a new post for the current user.""" if request.method == "post": title = request.form["title"] body = request.form["body"] error = none if not title: error = "title is required." if error is not none: flash(error) else: db = get_db() db.execute( "insert into post (title, body, author_id) values (?, ?, ?)", (title, body, g.user["id"]), ) db.commit() return redirect(url_for("blog.index")) return render_template("blog/create.html")
更新和删除博客
更新和删除博客,需要传入一个 id,然后有一个内部函数用于判断该 id 是否存在:
def get_post(id, check_author=true): """get a post and its author by id. checks that the id exists and optionally that the current user is the author. :param id: id of post to get :param check_author: require the current user to be the author :return: the post with author information :raise 404: if a post with the given id doesn't exist :raise 403: if the current user isn't the author """ post = ( get_db() .execute( "select p.id, title, body, created, author_id, username" " from post p join user u on p.author_id = u.id" " where p.id = ?", (id,), ) .fetchone() ) if post is none: abort(404, f"post id {id} doesn't exist.") if check_author and post["author_id"] != g.user["id"]: abort(403) return post
因此,更新的逻辑如下:
@bp.route("/<int:id>/update", methods=("get", "post")) @login_required def update(id): """update a post if the current user is the author.""" post = get_post(id) if request.method == "post": title = request.form["title"] body = request.form["body"] error = none if not title: error = "title is required." if error is not none: flash(error) else: db = get_db() db.execute( "update post set title = ?, body = ? where id = ?", (title, body, id) ) db.commit() return redirect(url_for("blog.index")) return render_template("blog/update.html", post=post)
删除的逻辑如下:
@bp.route("/<int:id>/delete", methods=("post",)) @login_required def delete(id): """delete a post. ensures that the post exists and that the logged in user is the author of the post. """ get_post(id) db = get_db() db.execute("delete from post where id = ?", (id,)) db.commit() return redirect(url_for("blog.index"))
4.其他
其他还有一些,是大家玩熟了之后才需要看的:
- 工程部署安装
- 工程自动化测试
5.跑起 demo
最后,我们跑起 demo 看看效果:
1)在 tutorial 目录下,创建虚拟环境,并安装 flask:
python3 -m venv venv . venv/bin/activate pip install flask
2)以开发者方式运行:
export flask_app=flaskr export flask_env=development flask init-db flask run
效果如下:
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