Python如何使用Web框架Flask開發項目

$ sudo pip3 install Flask

$ python3
 
>>> import flask
>>> print(flask.__doc__)
 
    flask
    ~~~~~
 
    A microframework based on Werkzeug.  It's extensively documented
    and follows best practice patterns.
 
    :copyright: © 2010 by the Pallets team.
    :license: BSD, see LICENSE for more details.
 
>>> print(flask.__version__)
1.0.2

from flask import Flask
 
app = Flask(__name__)
 
@app.route('/')
def hello_world():
    return 'Hello World!'
 
if __name__ == '__main__':
    app.run()

$ python3 server.py 
 * Running on http://127.0.0.1:5000/

127.0.0.1 - - [16/May/2014 10:29:08] "GET / HTTP/1.1" 200 -

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

app = Flask(__name__)

app = Flask("my-app", static_folder="path2", template_folder="path3")

from flask import Flask
print(Flask.__doc__)

app.run(debug=True)

app.run(host='0.0.0.0', port=80, debug=True)

$ sudo python3 server.py

from flask import Flask, request
 
app = Flask(__name__)
 
 
@app.route('/')
def hello_world():
    return request.args.__str__()
 
 
if __name__ == '__main__':
    app.run(port=5000, debug=True)

ImmutableMultiDict([('user', 'Flask'), ('time', ''), ('p', '7'), ('p', '8')])

ImmutableMultiDict([('info', '这是爱，')])

from flask import Flask, request
 
app = Flask(__name__)
 
 
@app.route('/')
def hello_world():
    print(request.path)
    print(request.full_path)
    return request.args.__str__()
 
 
if __name__ == '__main__':
    app.run(port=5000, debug=True)

from flask import Flask, request
 
app = Flask(__name__)
 
@app.route('/')
def hello_world():
    return request.args.get('info')
 
if __name__ == '__main__':
    app.run(port=5000)

hello

from flask import Flask, request
 
app = Flask(__name__)
 
@app.route('/')
def hello_world():
    r = request.args.get('info')
    if r==None:
        # do something
        return ''
    return r
 
if __name__ == '__main__':
    app.run(port=5000, debug=True)

from flask import Flask, request
 
app = Flask(__name__)
 
@app.route('/')
def hello_world():
    r = request.args.get('info', 'hi')
    return r
 
if __name__ == '__main__':
    app.run(port=5000, debug=True)

hi

from flask import Flask, request
 
app = Flask(__name__)
 
@app.route('/')
def hello_world():
    r = request.args.get('p')
    return r
 
if __name__ == '__main__':
    app.run(port=5000, debug=True)

from flask import Flask, request
 
app = Flask(__name__)
 
 
@app.route('/')
def hello_world():
    r = request.args.getlist('p')  # 返回一个list
    return str(r)
 
 
if __name__ == '__main__':
    app.run(port=5000, debug=True)

$ sudo pip3 install requests

from flask import Flask, request
 
app = Flask(__name__)
 
 
@app.route('/')
def hello_world():
    return 'hello world'
 
 
@app.route('/register', methods=['POST'])
def register():
    print(request.headers)
    print(request.stream.read())
    return 'welcome'
 
 
if __name__ == '__main__':
    app.run(port=5000, debug=True)

@app.route('/register', methods=['GET', 'POST'])

import requests
 
user_info = {'name': 'letian', 'password': '123'}
r = requests.post("http://127.0.0.1:5000/register", data=user_info)
 
print(r.text)

welcome

Host: 127.0.0.1:5000
User-Agent: python-requests/2.19.1
Accept-Encoding: gzip, deflate
Accept: */*
Connection: keep-alive
Content-Length: 24
Content-Type: application/x-www-form-urlencoded
 
 
b'name=letian&password=123'

b'name=letian&password=123'

b'name=letian&password=123'

from flask import Flask, request
 
app = Flask(__name__)
 
@app.route('/')
def hello_world():
    return 'hello world'
 
 
@app.route('/register', methods=['POST'])
def register():
    print(request.headers)
    # print(request.stream.read()) # 不要用，否则下面的form取不到数据
    print(request.form)
    print(request.form['name'])
    print(request.form.get('name'))
    print(request.form.getlist('name'))
    print(request.form.get('nickname', default='little apple'))
    return 'welcome'
 
 
if __name__ == '__main__':
    app.run(port=5000, debug=True)

Host: 127.0.0.1:5000
User-Agent: python-requests/2.19.1
Accept-Encoding: gzip, deflate
Accept: */*
Connection: keep-alive
Content-Length: 24
Content-Type: application/x-www-form-urlencoded
 
 
ImmutableMultiDict([('name', 'letian'), ('password', '123')])
letian
letian
['letian']
little apple

print(request.form.get('nickname', default='little apple'))

little apple

import requests
 
user_info = {'name': ['letian', 'letian2'], 'password': '123'}
r = requests.post("http://127.0.0.1:5000/register", data=user_info)
 
print(r.text)

[u'letian', u'letian2']

from flask import Flask, request
 
app = Flask("my-app")
 
 
@app.route('/')
def hello_world():
    return 'Hello World!'
 
 
@app.route('/add', methods=['POST'])
def add():
    print(request.headers)
    print(type(request.json))
    print(request.json)
    result = request.json['a'] + request.json['b']
    return str(result)
 
 
if __name__ == '__main__':
    app.run(host='127.0.0.1', port=5000, debug=True)

import requests
 
json_data = {'a': 1, 'b': 2}
 
r = requests.post("http://127.0.0.1:5000/add", json=json_data)
 
print(r.text)

3

Host: 127.0.0.1:5000
User-Agent: python-requests/2.19.1
Accept-Encoding: gzip, deflate
Accept: */*
Connection: keep-alive
Content-Length: 16
Content-Type: application/json
 
 

{'a': 1, 'b': 2}

from flask import Flask, request, Response
import json
 
app = Flask("my-app")
 
 
@app.route('/')
def hello_world():
    return 'Hello World!'
 
 
@app.route('/add', methods=['POST'])
def add():
    result = {'sum': request.json['a'] + request.json['b']}
    return Response(json.dumps(result),  mimetype='application/json')
 
 
if __name__ == '__main__':
    app.run(host='127.0.0.1', port=5000, debug=True)

import requests
 
json_data = {'a': 1, 'b': 2}
 
r = requests.post("http://127.0.0.1:5000/add", json=json_data)
 
print(r.headers)
print(r.text)

{'Content-Type': 'application/json', 'Content-Length': '10', 'Server': 'Werkzeug/0.14.1 Python/3.6.4', 'Date': 'Sat, 07 Jul 2018 05:23:00 GMT'}

{"sum": 3}

@app.route('/add', methods=['POST'])
def add():
    result = {'sum': request.json['a'] + request.json['b']}
    resp = Response(json.dumps(result),  mimetype='application/json')
    resp.headers.add('Server', 'python flask')
    return resp

{'Content-Type': 'application/json', 'Content-Length': '10', 'Server': 'python flask', 'Date': 'Sat, 07 Jul 2018 05:26:40 GMT'}

{"sum": 3}

from flask import Flask, request, jsonify
 
app = Flask("my-app")
 
 
@app.route('/')
def hello_world():
    return 'Hello World!'
 
 
@app.route('/add', methods=['POST'])
def add():
    result = {'sum': request.json['a'] + request.json['b']}
    return jsonify(result)
 
 
if __name__ == '__main__':
    app.run(host='127.0.0.1', port=5000, debug=True)

mkdir HelloWorld/static/uploads

$ sudo pip3 install werkzeug

from flask import Flask, request
 
from werkzeug.utils import secure_filename
import os
 
app = Flask(__name__)
 
# 文件上传目录
app.config['UPLOAD_FOLDER'] = 'static/uploads/'
# 支持的文件格式
app.config['ALLOWED_EXTENSIONS'] = {'png', 'jpg', 'jpeg', 'gif'}  # 集合类型
 
 
# 判断文件名是否是我们支持的格式
def allowed_file(filename):
    return '.' in filename and \
           filename.rsplit('.', 1)[1] in app.config['ALLOWED_EXTENSIONS']
 
 
@app.route('/')
def hello_world():
    return 'hello world'
 
 
@app.route('/upload', methods=['POST'])
def upload():
    upload_file = request.files['image']
    if upload_file and allowed_file(upload_file.filename):
        filename = secure_filename(upload_file.filename)
        # 将文件保存到 static/uploads 目录，文件名同上传时使用的文件名
        upload_file.save(os.path.join(app.root_path, app.config['UPLOAD_FOLDER'], filename))
        return 'info is '+request.form.get('info', '')+'. success'
    else:
        return 'failed'
 
 
if __name__ == '__main__':
    app.run(port=5000, debug=True)

import requests
file_data = {'image': open('Lenna.jpg', 'rb')}
user_info = {'info': 'Lenna'}
r = requests.post("http://127.0.0.1:5000/upload", data=user_info, files=file_data)
print(r.text)

app.config['MAX_CONTENT_LENGTH'] = 16 * 1024 * 1024 #16MB

file_content = request.files['image'].stream.read()

from flask import Flask
 
app = Flask(__name__)
 
 
@app.route('/')
def hello_world():
    return 'hello world'
 
 
@app.route('/user/')
def user(username):
    print(username)
    print(type(username))
    return 'hello ' + username
 
 
@app.route('/user//friends')
def user_friends(username):
    print(username)
    print(type(username))

    return 'hello ' + username
 
 
if __name__ == '__main__':
    app.run(port=5000, debug=True)

Hello letian. They are your friends.

from flask import Flask
 
app = Flask(__name__)
 
 
@app.route('/')
def hello_world():
    return 'hello world'
 
 
@app.route('/page/')
def page(num):
    print(num)
    print(type(num))
    return 'hello world'
 
 
if __name__ == '__main__':
    app.run(port=5000, debug=True)

1

int     accepts integers

float     like int but for floating point values

path     like the default but also accepts slashes

from flask import Flask
 
app = Flask(__name__)
 
 
@app.route('/')
def hello_world():
    return 'hello world'
 
 
@app.route('/page/-')
def page(num1, num2):
    print(num1)
    print(num2)
    return 'hello world'
 
 
if __name__ == '__main__':
    app.run(port=5000, debug=True)

11

22

from flask import Flask, url_for
 
from werkzeug.routing import BaseConverter
 
 
class MyIntConverter(BaseConverter):
 
    def __init__(self, url_map):
        super(MyIntConverter, self).__init__(url_map)
 
    def to_python(self, value):
        return int(value)
 
    def to_url(self, value):
        return value * 2
 
 
app = Flask(__name__)
app.url_map.converters['my_int'] = MyIntConverter
 
 
@app.route('/')
def hello_world():
    return 'hello world'
 
 
@app.route('/page/')
def page(num):
    print(num)
    print(url_for('page', num=123))   # page 对应的是 page函数 ，num 对应对应`/page/`中的num，必须是str
    return 'hello world'
 
 
if __name__ == '__main__':
    app.run(port=5000, debug=True)

123

/page/123123

from flask import Flask, url_for
 
app = Flask(__name__)
 
@app.route('/')
def hello_world():
    pass
 
@app.route('/user/')
def user(name):
    pass
 
@app.route('/page/')
def page(num):
    pass
 
@app.route('/test')
def test():
    print(url_for('hello_world'))
    print(url_for('user', name='letian'))
    print(url_for('page', num=1, q='hadoop mapreduce 10%3'))
    print(url_for('static', filename='uploads/01.jpg'))
    return 'Hello'
 
if __name__ == '__main__':
    app.run(debug=True)

/
/user/letian
/page/1?q=hadoop+mapreduce+10%253
/static/uploads/01.jpg

from flask import Flask, url_for, redirect
 
app = Flask(__name__)
 
@app.route('/')
def hello_world():
    return 'hello world'
 
@app.route('/test1')
def test1():
    print('this is test1')
    return redirect(url_for('test2'))
 
@app.route('/test2')
def test2():
    print('this is test2')
    return 'this is test2'
 
if __name__ == '__main__':
    app.run(debug=True)

this is test2

<html>
<head>
    <title>
        {% if page_title %}
            {{ page_title }}
        {% endif %}
    </title>
</head>
 
<body>
    {% block body %}{% endblock %}
 
 
```
可以看到，在``标签中使用了if判断，如果给模板传递了`page_title`变量，显示之，否则，不显示。
``标签中定义了一个名为`body`的block，用来被其他模板文件继承。
### 11.3 创建并编辑HelloWorld/templates/user_info.html
内容如下：
```
{% extends "default.html" %}
 
{% block body %}
    {% for key in user_info %}
 
        {{ key }}: {{ user_info[key] }} 
 
 
    {% endfor %}
{% endblock %}

from flask import Flask, render_template
 
app = Flask(__name__)
 
 
@app.route('/')
def hello_world():
    return 'hello world'
 
 
@app.route('/user')
def user():
    user_info = {
        'name': 'letian',
        'email': '123@aa.com',
        'age':0,
        'github': 'https://github.com/letiantian'
    }
    return render_template('user_info.html', page_title='letian\'s info', user_info=user_info)
 
 
if __name__ == '__main__':
    app.run(port=5000, debug=True)

$ python3 HelloWorld/server.py

<html>
<head>
    <title>
            letian&&9;s info
    </title>
</head>
<body>
        name: letian <br/>
        email: 123@aa.com <br/>
        age: 0 <br/>
        github: https://github.com/letiantian <br/>
</body>
</html>

from flask import Flask, render_template_string, abort
 
app = Flask(__name__)
 
 
@app.route('/')
def hello_world():
    return 'hello world'
 
 
@app.route('/user')
def user():
    abort(401)  # Unauthorized 未授权
    print('Unauthorized, 请先登录')
 
 
if __name__ == '__main__':
    app.run(port=5000, debug=True)

from flask import Flask, render_template_string, abort
 
app = Flask(__name__)
 
 
@app.route('/')
def hello_world():
    return 'hello world'
 
 
@app.route('/user')
def user():
    abort(401)  # Unauthorized
 
 
@app.errorhandler(401)
def page_unauthorized(error):
    return render_template_string('
 Unauthorized 
{{ error_info }}', error_info=error), 401
 
 
if __name__ == '__main__':
    app.run(port=5000, debug=True)

from flask import Flask, render_template_string, \
    session, request, redirect, url_for
 
app = Flask(__name__)
 
app.secret_key = 'F12Zr47j\3yX R~X@H!jLwf/T'
 
 
@app.route('/')
def hello_world():
    return 'hello world'
 
 
@app.route('/login')
def login():
     return render_template_string(page)
@app.route('/do_login', methods=['POST'])
def do_login():
    name = request.form.get('user_name')
    session['user_name'] = name
    return 'success'
 
 
@app.route('/show')
def show():
    return session['user_name']
 
 
@app.route('/logout')
def logout():
    session.pop('user_name', None)
    return redirect(url_for('login'))
 
 
if __name__ == '__main__':
    app.run(port=5000, debug=True)

from datetime import timedelta
from flask import session, app
 
session.permanent = True
app.permanent_session_lifetime = timedelta(minutes=5)

from flask import Flask, request, Response, make_response
import time
 
app = Flask(__name__)
 
 
@app.route('/')
def hello_world():
    return 'hello world'
 
 
@app.route('/add')
def login():
    res = Response('add cookies')
    res.set_cookie(key='name', value='letian', expires=time.time()+6*60)
    return res
 
 
@app.route('/show')
def show():
    return request.cookies.__str__()
 
 
@app.route('/del')
def del_cookie():
    res = Response('delete cookies')
    res.set_cookie('name', '', expires=0)
    return res
 
 
if __name__ == '__main__':
    app.run(port=5000, debug=True)

res.set_cookie(key='name', value='letian', expires=time.time()+6*60)

res.set_cookie('name', '', expires=0)

add cookies

Set-Cookie: name=letian; Expires=Sun, 29-Jun-2014 05:16:27 GMT; Path=/

{'name': 'letian'}

from flask import Flask, flash, get_flashed_messages
import time
 
app = Flask(__name__)
app.secret_key = 'some_secret'
 
 
@app.route('/')
def index():
    return 'hi'
 
 
@app.route('/gen')
def gen():
    info = 'access at '+ time.time().__str__()
    flash(info)
    return info
 
 
@app.route('/show1')
def show1():
    return get_flashed_messages().__str__()
 
 
@app.route('/show2')
def show2():
    return get_flashed_messages().__str__()
 
 
if __name__ == "__main__":
    app.run(port=5000, debug=True)

access at 1404020982.83

.eJyrVopPy0kszkgtVrKKrlZSKIFQSUpWSknhYVXJRm55UYG2tkq1OlDRyHC_rKgIvypPdzcDTxdXA1-XwHLfLEdTfxfPUn8XX6DKWCAEAJKBGq8.BpE6dg.F1VURZa7VqU9bvbC4XIBO9-3Y4Y

access at 1404021130.32

.eJyrVopPy0kszkgtVrKKrlZSKIFQSUpWSknhYVXJRm55UYG2tkq1OlDRyHC_rKgIvypPdzcDTxdXA1-XwHLfLEdTfxfPUn8XX6DKWLBaMg1yrfCtciz1rfIEGxRbCwAhGjC5.BpE7Cg.Cb_B_k2otqczhknGnpNjQ5u4dqw

['access at 1404020982.83', 'access at 1404021130.32']

[]

from flask import Flask, flash, get_flashed_messages
import time
 
app = Flask(__name__)
app.secret_key = 'some_secret'
 
 
@app.route('/')
def index():
    return 'hi'
 
 
@app.route('/gen')
def gen():
    info = 'access at '+ time.time().__str__()
    flash('show1 '+info, category='show1')
    flash('show2 '+info, category='show2')
    return info
 
 
@app.route('/show1')
def show1():
    return get_flashed_messages(category_filter='show1').__str__()
 
@app.route('/show2')
def show2():
    return get_flashed_messages(category_filter='show2').__str__()
 
 
if __name__ == "__main__":
    app.run(port=5000, debug=True)

access at 1404022326.39

['1 access at 1404022326.39']

[]