flask框架

一.入门

1.demo

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from flask import Flask
app = Flask(__name__)

@app.route('/')
def hello_world():
    return 'Hello, World!'

2.可变参数

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@app.route('/<user>')
def hello_world(user):
    return 'Hello {}'.format(user)

image-20210408102134741

3.唯一url和重定向

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// @app.route('/project') @app.route('/project/')
def projects():
    return 'project1'

4.url_for()

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from flask import Flask, url_for
from markupsafe import escape

app = Flask(__name__)

@app.route('/')
def index():
    return 'index'

@app.route('/login')
def login():
    return 'login'

@app.route('/user/<username>')
def profile(username):
    return '{}\'s profile'.format(escape(username))

with app.test_request_context():
    print(url_for('index'))
    print(url_for('login'))
    print(url_for('login', next='/'))
    print(url_for('profile', username='John Doe'))
    
    
 # 静态文件:
    url_for('static', filename='style.css')

5.http方法

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from flask import request

@app.route('/login', methods=['GET', 'POST'])
def login():
    if request.method == 'POST':
        return do_the_login()
    else:
        return show_the_login_form()

    # 获取提交的数据
    User = request.args.get(‘nm’)
	user = request.form['nm']

6.模板

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from flask import render_template

@app.route('/hello/')
@app.route('/hello/<name>')
def hello(name=None):
    return render_template('hello.html', name=name)
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<!doctype html>
<title>Hello from Flask</title>
{% if name %}
  <h1>Hello {{ name }}!</h1>
{% else %}
  <h1>Hello, World!</h1>
{% endif %}
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# 设置
resp = make_response("success")   # 设置响应体
resp.set_cookie("w3cshool", "w3cshool", max_age=3600)

# 获取
cookie_1 = request.cookies.get("w3cshool")

# 删除
resp = make_response("del success")  # 设置响应体
resp.delete_cookie("w3cshool")

# 实例
from flask import Flask, make_response, request

app = Flask(__name__)

@app.route("/set_cookies")
def set_cookie():
    resp = make_response("success")
    resp.set_cookie("w3cshool", "w3cshool",max_age=3600)
    return resp

@app.route("/get_cookies")
def get_cookie():
    cookie_1 = request.cookies.get("w3cshool")  # 获取名字为Itcast_1对应cookie的值
    return cookie_1

@app.route("/delete_cookies")
def delete_cookie():
    resp = make_response("del success")
    resp.delete_cookie("w3cshool")

    return resp

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

8.session

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# 设置
Session[‘username’] = ’admin’
# 释放
session.pop('username', None)
#

9.重定向和错误

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from flask import Flask, redirect, url_for, render_template, request
# Initialize the Flask application
app = Flask(__name__)

@app.route('/')
def index():
   return render_template('log_in.html')

@app.route('/login',methods = ['POST', 'GET'])
def login():
   if request.method == 'POST' and
       request.form['username'] == 'admin' :
           return redirect(url_for('success'))
           return redirect(url_for('index'))

@app.route('/success')
def success():
   return 'logged in successfully'
	
if __name__ == '__main__':
   app.run(debug = True)
# 错误
from flask import Flask, redirect, url_for, render_template, request, abort
app = Flask(__name__)

@app.route('/')
def index():
   return render_template('log_in.html')

@app.route('/login',methods = ['POST', 'GET'])
def login():
   if request.method == 'POST':
      if request.form['username'] == 'admin' :
         return redirect(url_for('success'))
      else:
         abort(401)
   else:
      return redirect(url_for('index'))

@app.route('/success')
def success():
   return 'logged in successfully'

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

9.文件上传

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<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>
# python代码
from flask import Flask, render_template, request
from werkzeug.utils import secure_filename
import os

app = Flask(__name__)
app.config['UPLOAD_FOLDER'] = 'upload/'

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

@app.route('/uploader', methods = ['GET', 'POST'])
def uploader():
   if request.method == 'POST':
      f = request.files['file']
      f.save(os.path.join(app.config['UPLOAD_FOLDER'],secure_filename(f.filename)))
      return 'file uploaded successfully'

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