Python3+Flask初学教程

比眉伴天荒 2022-11-06 05:48 243阅读 0赞

**目录**

一、学习文档

二、项目结构

三、项目文件

四、效果展示

1、登录页面

2、首页页面

3、上传文件

4、查询数据库

5、404页面

--------------------

## 一、学习文档 ##

Flask 依赖 [Jinja][] 模板引擎和 [Werkzeug][] WSGI 套件

W3Cschool：[https://www.w3cschool.cn/flask/][https_www.w3cschool.cn_flask]

Flask中文文档：[https://dormousehole.readthedocs.io/en/latest/][https_dormousehole.readthedocs.io_en_latest]

Jinja2 模板文档：[https://jinja.palletsprojects.com/en/2.11.x/templates/][https_jinja.palletsprojects.com_en_2.11.x_templates]

Werkzeug 文档：[https://werkzeug.palletsprojects.com/en/1.0.x/][https_werkzeug.palletsprojects.com_en_1.0.x]

Flask应用功能扩展：[https://dormousehole.readthedocs.io/en/latest/extensions.html\#extensions][https_dormousehole.readthedocs.io_en_latest_extensions.html_extensions]

Flask生产环境部署：[https://dormousehole.readthedocs.io/en/latest/deploying/index.html\#deployment][https_dormousehole.readthedocs.io_en_latest_deploying_index.html_deployment]

## 二、项目结构 ##

pycharm新建Flask项目之后添加或修改如下项目文件

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxMjYyNTkzNDIx_size_16_color_FFFFFF_t_70][]

## 三、项目文件 ##

**404.html**

<h1>404 error</h1>
        <a href = "{
       { url_for('index') }}">index</a> <br/>

**hello.html**

<title>Hello from Flask</title>
    {% if name %}
      <h1>Hello {
       { name }}!</h1>
    {% else %}
      <h1>Hello, World!</h1>
    {% endif %}
        <a href = "{
       { url_for('index') }}">index</a> <br/>

**index.html**

<!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>Welcome to Flask!</title>
        
        <script type = "text/javascript"
             src = "{
       { url_for('static', filename = 'js/hello.js') }}" ></script>
    </head>
    <body>
        <h1>Welcome to Flask!</h1>
        <input type = "button" onclick = "sayHello()" value = "Say Hello" />
        {% with messages = get_flashed_messages() %}
             {% if messages %}
                   {% for message in messages %}
                        <p>{
       { message }}</p>
                   {% endfor %}
             {% endif %}
        {% endwith %}
        <a href = "{
       { url_for('set_cookie') }}">set_cookie</a> <br/>
        <a href = "{
       { url_for('get_cookie') }}">get_cookie</a> <br/>
        <a href = "{
       { url_for('del_cookie') }}">del_cookie</a> <br/>
        <a href = "{
       { url_for('login') }}">login</a> <br/>
        <a href = "{
       { url_for('upload_file') }}">upload</a> <br/>
        <a href = "student.html">student</a> <br/>
        <b><a href = 'mysqldb.html'>mysqldb</a></b> <br/>
        <b><a href = "{
       { url_for('logout') }}">点击这里注销</a></b> <br/>
        <a href = "404.html">404</a> <br/>
    </body>
    </html>

**kv-result.html**

<table border = 1>
         {% for key, value in result.items() %}
        <tr>
           <th> {
       { key }} </th>
           <td> {
       { value }}</td>
        </tr>
     {% endfor %}
      </table>
      <a href = "{
       { url_for('index') }}">index</a> <br/>

**login.html**

<!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>Login</title>
    </head>
    <body>
        <form method = "post" action = "http://localhost:5000/login">
            <table>
                <tr>
                    <td>Username</td>
                    <td><input type = 'username' name = 'username'></td>
                </tr>
                <tr>
                    <td>Password</td>
                    <td><input type = 'password' name = 'password'></td>
                </tr>
                <tr>
                    <td><input type = "submit" value = "Submit"></td>
                </tr>
            </table>
        </form>
        {% if error %}
            <p><strong>Error</strong>: {
       { error }}</p>
        {% endif %}
    </body>
    </html>

**mysqldb.html**

<!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>mysql_db</title>
    </head>
    <body>
      <form action="/mysql_db" method="POST">
         <p>ip:<input type="text" name="ip" value="127.0.0.1"/></p>
         <p>port:<input type="text" name="port" value="3306"/></p>
         <p>username:<input type="text" name="username" value="root"/></p>
         <p>password:<input type="text" name="password" value="123456"/></p>
         <p><input type="submit" value="submit" /></p>
      </form>
        <a href = "{
       { url_for('index') }}">index</a> <br/>
    </body>
    </html>

**result.html**

<!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>Title</title>
    </head>
    <body>
      <table border = 1>
         {% for value in result %}
        <tr>
    {#       <th> {
       { key }} </th>#}
           <td> {
       { value }}</td>
        </tr>
     {% endfor %}
      </table>
      <a href = "{
       { url_for('index') }}">index</a> <br/>
    </body>
    </html>

**student.html**

<form action="/kv-result" method="POST">
         <p>Name <input type = "text" name = "Name" value = "Name" /></p>
         <p>Physics <input type = "text" name = "Physics" value = "Physics" /></p>
         <p>Chemistry <input type = "text" name = "chemistry" value = "chemistry" /></p>
         <p>Maths <input type ="text" name = "Mathematics" value = "Mathematics" /></p>
         <p><input type = "submit" value = "submit" /></p>
      </form>

**upload.html**

<h1>Upload new File</h1>
        <form method=post enctype=multipart/form-data>
          <input type=file name=file>
          <input type=submit value=Upload>
        </form>
        <a href = "{
       { url_for('index') }}">index</a> <br/>

**app.py**

import os, json
    from flask import Flask, render_template, flash, request, redirect, jsonify, session
    from flask import escape, url_for, make_response, abort
    from werkzeug.utils import secure_filename
    from utils.db.MySQLUtil import MySQLUtil
    
    UPLOAD_FOLDER = './'
    ALLOWED_EXTENSIONS = {'txt', 'log', 'pdf', 'png', 'jpg', 'jpeg', 'gif'}
    app = Flask(__name__)
    
    app.config['UPLOAD_FOLDER'] = UPLOAD_FOLDER
    app.config['MAX_CONTENT_LENGTH'] = 16 * 1024 * 1024
    
    app.secret_key = 'A0Zr98j/3yX R~XHH!jmN]LWX/,?RT'
    
    @app.route('/index', methods=['GET', 'POST'])
    def index():
        """请求方法和cookie"""
        method = request.method
        username = request.cookies.get('username')
        print(method, username)
        return render_template('index.html', name="name_welcome")
    
    @app.route('/hello/')
    @app.route('/hello/<name>')
    def hello(name=None):
        """变量规则"""
        return render_template('hello.html', name=name)
    
    def allowed_file(filename):
        return '.' in filename and \
               filename.rsplit('.', 1)[1].lower() in ALLOWED_EXTENSIONS
    
    @app.route('/upload', methods=['GET', 'POST'])
    def upload_file():
        """文件上传"""
        if request.method == 'POST':
            # check if the post request has the file part
            if 'file' not in request.files:
                flash('No file part')
                return redirect(request.url)
            file = request.files['file']
            # if user does not select file, browser also
            # submit an empty part without filename
            if file.filename == '':
                flash('No selected file')
                return render_template('upload.html')
            if file and allowed_file(file.filename):
                filename = secure_filename(file.filename)
                file.save(os.path.join(app.config['UPLOAD_FOLDER'], filename))
                flash('upload file success')
                return url_for('upload_file', filename=filename)
        return render_template('upload.html')
    
    @app.route('/match/<str>')
    def match_url(str):
        """url构建"""
        print('{}\'s profile'.format(escape(str)))
        return render_template(str+".html")
    
    @app.route('/<str>')
    def url_forward(str):
        """url构建"""
        return render_template(str)
    
    @app.route('/set_cookie')
    def set_cookie():
        """存储cookie"""
        response = make_response("set cookie success")
        response.set_cookie('username', 'the username')
        flash(str(response))
        return redirect(url_for('index'))
    
    @app.route('/get_cookie')
    def get_cookie():
        """读取cookie"""
        cookie = request.cookies.get('username')
        flash(cookie)
        return redirect(url_for('index'))
    
    @app.route("/del_cookie")
    def del_cookie():
        """删除cookie（删除只是让cookie过期）"""
        response = make_response("delete cookie success")
        response.delete_cookie("username")
        flash(str(response))
        return redirect(url_for('index'))
    
    @app.route('/')
    def my_redirect():
        return redirect(url_for('login'))
    
    @app.errorhandler(404)
    def page_not_found(error):
        """404状态返回网页"""
        return render_template('404.html'), 404
    
    @app.route('/login', methods = ['GET', 'POST'])
    def login():
        """消息闪现"""
        error = None
        if request.method == 'POST':
            if request.form['username'] != 'admin': ## or request.form['password'] != 'admin':
               error = "Invalid username or password. Please try again!"
            else:
               flash('You were successfully logged in')
               return redirect(url_for('index'))
        return render_template('login.html', error=error)
    
    @app.route('/logout')
    def logout():
        """删除session中的username"""
        session.pop('username', None)
        return redirect(url_for('login'))
    
    @app.route('/kv-result', methods=['POST', 'GET'])
    def result():
        """将表单数据返回给模板"""
        if request.method == 'POST':
          result = request.form
          print(result)
          return render_template("kv-result.html", result=result)
    
    @app.route('/mysql_db', methods=['POST', 'GET'])
    def mysql_db():
        """查询MySQL全部数据库名称"""
        if request.method == 'POST':
          form = request.form
          print(type(form), form)
          ip = form['ip']
          port = form['port']
          username = form['username']
          password = form['password']
          print(ip, port, username, password)
          mysqlUtil = MySQLUtil(ip, port, username, password)
          dbs = mysqlUtil.list_databases()
          print(dbs)
          return render_template("result.html", result=dbs)
    
    if __name__ == '__main__':
        print(1111)
        app.run(host='0.0.0.0', port='5000', debug=True, threaded=True)
        app.logger.debug('A value for debugging')
        app.logger.warning('A warning occurred (%d apples)', 42)
        app.logger.error('An error occurred')
        print(2222)

**flash.py**

#-*- encoding: utf-8 -*-
    
    from flask import Flask, flash, redirect, render_template, request, url_for
    app = Flask(__name__)
    
    app.secret_key = 'random string'
    
    @app.route('/')
    def index():
        return render_template('index.html')
    
    @app.route('/login', methods = ['GET', 'POST'])
    def login():
        error = None
        if request.method == 'POST':
            if request.form['username'] != 'admin' or \
                request.form['password'] != 'admin':
                error = 'Invalid username or password. Please try again!'
            else:
                flash('You were successfully logged in')
                return redirect(url_for('index'))
        return render_template('login.html', error=error)
    
    if __name__ == "__main__":
        app.run(debug=True)

## 四、效果展示 ##

执行 app.py 启动程序，浏览器访问 [http://127.0.0.1:5000/login][http_127.0.0.1_5000_login]

### 1、登录页面 ###

输入用户名：admin（密码随意）

![20210308195449859.png][]

### 2、首页页面 ###

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxMjYyNTkzNDIx_size_16_color_FFFFFF_t_70 1][]

### **3、上传文件** ###

![20210308195603124.png][]

### 4、查询数据库 ###

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxMjYyNTkzNDIx_size_16_color_FFFFFF_t_70 2][]![20210308195633130.png][]

### **5、404页面** ###

![20210308195657366.png][]

[Jinja]: https://www.palletsprojects.com/p/jinja/
[Werkzeug]: https://www.palletsprojects.com/p/werkzeug/
[https_www.w3cschool.cn_flask]: https://www.w3cschool.cn/flask/
[https_dormousehole.readthedocs.io_en_latest]: https://dormousehole.readthedocs.io/en/latest/
[https_jinja.palletsprojects.com_en_2.11.x_templates]: https://jinja.palletsprojects.com/en/2.11.x/templates/
[https_werkzeug.palletsprojects.com_en_1.0.x]: https://werkzeug.palletsprojects.com/en/1.0.x/
[https_dormousehole.readthedocs.io_en_latest_extensions.html_extensions]: https://dormousehole.readthedocs.io/en/latest/extensions.html#extensions
[https_dormousehole.readthedocs.io_en_latest_deploying_index.html_deployment]: https://dormousehole.readthedocs.io/en/latest/deploying/index.html#deployment
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxMjYyNTkzNDIx_size_16_color_FFFFFF_t_70]: /images/20221023/1174df13f05e406dacd5f3b50081c854.png
[http_127.0.0.1_5000_login]: http://127.0.0.1:5000/login
[20210308195449859.png]: /images/20221023/834c305c73014207a08a7f28ccf7ef1c.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxMjYyNTkzNDIx_size_16_color_FFFFFF_t_70 1]: /images/20221023/d9bc9590506d4ad9810467e985c866d0.png
[20210308195603124.png]: /images/20221023/c0aaa0aecc764a6280c952cf534dc255.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxMjYyNTkzNDIx_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/20210308195625806.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxMjYyNTkzNDIx,size_16,color_FFFFFF,t_70
[20210308195633130.png]: /images/20221023/d8031798d8cd4b25a66136a57bb365b4.png
[20210308195657366.png]: /images/20221023/9abde7a311a34d64ae367631efad1caf.png