flask学习进程

2021-01-26

flask闪现 flash

flash和get_flashed_messages()的关系是两者配合使用，flash就是在程序运行中实现交互，反馈信息。

flash(messages,categories)，flash函数具有两个参数：

第一个参数是你将要放进去的字符串消息。
第二个默认参数category，代表消息的类别，默认为message（消息，普通）。

get_flashed_messages(with_categories, category_filter) 两个默认参数

两个参数都是可选的。如果接收到的消息具有类别，则第一个参数是元组。第二个参数仅用于显示特定消息。

通常在路由规则的某个视图函数里调用flash函数，在与该视图函数渲染的模板html文件中，调用get_flashed_messages()获取flash函数传的message

flask上传下载文件

我写flask项目都是按自己的一套项目结构，而且这里都没用flask_migrate和flask_script，这里为了好演示，就全都写在一个py文件里。

app.py

import os

app = Flask(__name__)
app.secret_key = 'random string'

app.config['UPLOAD_FOLDER'] = '/Users/jueluo/upload/'
app.config['MAX_CONTENT_LENGTH'] = 16 * 1024 * 1024


@app.route('/upload')
def upload_file():
    return render_template('/user/upload.html')


@app.route('/uploader', methods=['GET', 'POST'])
def uploader():
    if request.method == 'POST':
        f = request.files['file']  # 2、upload.html当按下提交键后，通过request对象上的files获取文件。和以前用request获取表单值一样，使用input字段的name值获取：
        f.save(os.path.join(app.config['UPLOAD_FOLDER'], secure_filename(f.filename)))
        return 'file uploaded successfully'

      
@app.route('/downloads/<path:filename>', methods=['GET', 'POST'])  # filename 就是上传的文件的文件名 键入回车该url就可以下载文件
def download(filename):
    downloads = os.path.join(current_app.root_path, app.config['UPLOAD_FOLDER'])
    return send_from_directory(directory=downloads, filename=filename, as_attachment=True)


if __name__ == '__main__':
    app.run(debug=True)

index.html

<html>
<head>
  <title>File Upload</title>
</head>
<body>
    <form action="http://localhost:5000/uploader" method="POST" enctype="multipart/form-data">
        <input type="file" name="file" accept=".jpg,.png" />
        <input type="submit" />
    </form>
</body>
</html>

在这个内容的探索中，我才慢慢搞清楚render_template和redirect的区别，以及url_for()的参数。

render_template()模板渲染，请求到某个页面，将路由规则及视图函数和html挂钩。redirect(url_for())重定向函数，url_for(’’)参数为视图函数的名称，如果该视图函数名称过于复杂，可以在对应的路由规则上添加endpoint参数，url_for就传endpoint的值，就可以定位到这个函数。

sqlite

sqlite是一个python内置的数据库，我目前只会在pycharm里通过类似下面的命令创建一个spqlite数据库和对应表。然后在DATABASE处查看表结构。（可能之后会熟悉，之前用SQLAlchemy连接mysql，是自己在命令行里登录mysql，键入create database xxx charset=utf8;建好库，再在flask里定义好model类，创建表。而sqlite的数据库是一句sqlite3.connect('xxx.db')建立的）

sqlite创建库和表

import sqlite3

conn = sqlite3.connect('database.db')
print('Opened database successfully')
conn.execute('CREATE TABLE students (name TEXT, addr TEXT, city TEXT, pin TEXT)')
print("Table created successfully")
conn.close()

在进一步的摸索中，也解决了之前的疑惑，我一直以为 flask_sqlalchemy和sqlite是并列可替代关系，它们才不是呢。SQLAlchemy可以连接各类数据库，当然包括sqlite。

我要记录怎么连接sqlite，以及curd。

app.py

from flask import Flask, render_template, request, redirect, url_for
import sqlite3
import sqlite3 as sql
# 建库建表执行一次后记得去掉
conn = sqlite3.connect('database.db')
print('Opened database successfully')
conn.execute('CREATE TABLE students (name TEXT, addr TEXT, city TEXT, pin TEXT)')
print("Table created successfully")
conn.close()
app = Flask(__name__)


@app.route('/')
def home():
    return render_template('/sql/home.html')


@app.route('/enter', endpoint="enter")
def new_student():
    return render_template('/sql/student.html')


@app.route('/addrec', methods=['POST', 'GET'])
def addrec():
    if request.method == 'POST':
        try:
            nm = request.form['nm']
            addr = request.form['add']
            city = request.form['city']
            pin = request.form['pin']

            with sql.connect("database.db") as con:
                cur = con.cursor()

                cur.execute("INSERT INTO students (name,addr,city,pin)\
                VALUES(?,?,?,? )", (nm, addr, city, pin))

                con.commit()
                msg = "Record successfully added"
        except:
            con.rollback()
            msg = "error in insert operation"

        finally:
            return render_template("/sql/result.html", msg=msg)
            con.close()


@app.route('/delete', endpoint='delete')  # 测试了endpoint作用 调用下面函数时的别称
def de():
    conn = sqlite3.connect('database.db')
    c = conn.cursor()
    c.execute("DELETE from students where name='laoyike';")
    conn.commit()
    c.execute("select * from students")

    rows = c.fetchall()
    print("Total number of rows deleted :", conn.total_changes)
    return redirect(url_for('list'))
    # render_template没达到redirect的效果---》返回删除后最新的list
    # return render_template('/sql/list.html',rows=rows)


@app.route('/list', endpoint="list")
def list():
    con = sql.connect("database.db")
    con.row_factory = sql.Row

    cur = con.cursor()
    cur.execute("select * from students")

    rows = cur.fetchall()
    return render_template("/sql/list.html", rows=rows)


if __name__ == '__main__':
    app.run(debug=True)

home.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>HOME</title>
</head>
<body>
<h3>Welcome To Home!</h3>
<a href = "{{ url_for('enter') }}">enter</a><br>
<a href = "{{ url_for('list') }}">list</a><br>
<a href = "{{ url_for('delete') }}">delete</a>
</body>
</html>

list.html

<!doctype html>
<html>
   <body>

      <table border = 1>
         <thead>
            <td>Name</td>
            <td>Address</td>
            <td>city</td>
            <td>Pincode</td>
         </thead>

         {% for row in rows %}
            <tr>
               <td>{{row["name"]}}</td>
               <td>{{row["addr"]}}</td>
               <td> {{ row["city"]}}</td>
               <td>{{row['pin']}}</td>
            </tr>
         {% endfor %}
      </table>

      <a href = "/">Home</a>
      <a href="{{ url_for('enter') }}">enter</a>

   </body>
</html>

result.html

<!doctype html>
<html>
   <body>

      result of addition : {{ msg }}
      <h2><a href = "\">Home</a></h2>
   <br>
   <a href = "{{ url_for('list') }}">list</a>
{#    <a href="\list"></a>#}

   </body>
</html>

student.html

<html>
   <body>
      <form action = "{{ url_for('addrec') }}" method = "POST">
         <h3>Student Information</h3>
         Name
         <input type = "text" name = "nm" /></br>
         Address
         <textarea name = "add" ></textarea>
         City
         <input type = "text" name = "city" />
          PINCODE
          <input type = "text" name = "pin" />
         <input type = "submit" value = "submit" />
      </form>
   <a href="{{ url_for('list') }}">list</a>
{#   <a href="/list">list</a>  #}   {# 两者写法一致 #}
   </body>
</html>

flask_sqlalchemy

from flask import Flask, request, flash, url_for, redirect, render_template, send_from_directory, current_app
from flask_sqlalchemy import SQLAlchemy
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///january.db'  # 连接sqlite
# app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql+pymysql://root:12345678@127.0.0.1:3306/hi'  # 连接mysql

app.config['SECRET_KEY'] = "random string"

db = SQLAlchemy(app)


class students(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(100))
    city = db.Column(db.String(50))
    addr = db.Column(db.String(200))
    pin = db.Column(db.String(10))

    def __init__(self, name, city, addr, pin):
        self.name = name
        self.city = city
        self.addr = addr
        self.pin = pin


@app.route('/')
def show_all():
    # 可以借鉴已成功的flask03
    return render_template('/alchemy/show_all.html', students=students.query.all())


@app.route('/new', methods=['GET', 'POST'])
def new():
    if request.method == 'POST':
        if not request.form['name'] or not request.form['city'] or not request.form['addr']:
            flash('Please enter all the fields', 'error')
        else:
            student = students(request.form['name'], request.form['city'],
                               request.form['addr'], request.form['pin'])
            db.session.add(student)
            db.session.commit()
            flash('Record was successfully added')
            return redirect(url_for('show_all'))
    return render_template('/alchemy/new.html')

new.html

<!DOCTYPE html>
<html>
   <body>

      <h3>Students - Flask SQLAlchemy example</h3>
      <hr/>

      {% for category, message in get_flashed_messages(with_categories = true) %}
         <div class = "alert alert-danger">
            {{ message }}
         </div>
      {% endfor %}

      <form action = "{{ request.path }}" method = "post">
         <label for = "name">Name</label>
         <input type = "text" name = "name" placeholder = "Name" />
         <label for = "email">City</label>
         <input type = "text" name = "city" placeholder = "city" />
         <label for = "addr">addr</label>
         <textarea name = "addr" placeholder = "addr"></textarea>
         <label for = "PIN">City</label>
         <input type = "text" name = "pin" placeholder = "pin" />
         <input type = "submit" value = "Submit" />
      </form>
   </body>
</html>

show_all.html

<!DOCTYPE html>
<html lang = "en">
   <head></head>
   <body>

      <h3>
         <a href = "{{ url_for('show_all') }}">Comments - Flask SQLAlchemy example</a>
      </h3>
      <hr/>
      {% for message in get_flashed_messages() %}
         {{ message }}
      {% endfor %}

      <h3>Students (<a href = "{{ url_for('new') }}">Add Student </a>)</h3>

      <table>
         <thead>
            <tr>
               <th>Name</th>
               <th>City</th>
               <th>Address</th>
               <th>Pin</th>
            </tr>
         </thead>

         <tbody>
            {% for student in students %}
               <tr>
               <td>{{ student.id }}</td>
                  <td>{{ student.name }}</td>
                  <td>{{ student.city }}</td>
                  <td>{{ student.addr }}</td>
                  <td>{{ student.pin }}</td>
               </tr>
            {% endfor %}
         </tbody>
      </table>

   </body>
</html>