#Flask Quickstart
### 先建立專案資料夾
mkdir myproject
cd myproject
### 初始化
virtualenv env
### activate the corresponding environment
. venv/bin/activate
or
venv\scripts\activate
### 這時候再裝Flask
pip install Flask
### 回到實際環境
deactivate
### 若因為目錄搬移或更名 需重新locate
cd /path/to/your_project_new_dir
virtualenv --relocatable your_virtualenv_name
from flask import Flask
app = Flask(__name__)
@app.route('/')
def hello_world():
return 'Hello, World!'
# Unix Like:
export FLASK_APP=hello.py
python -m flask run
* Running on http://127.0.0.1:5000/
# Windows:
set FLASK_APP=hello.py
python -m flask run --host=0.0.0.0
* Running on http://127.0.0.1:5000/
# Debug Mode:
# export FLASK_DEBUG=1
程式範例：
@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 'User %s' % 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 'Post %d' % post_id
@app.route('/projects/')
def projects():
return 'The project page'
## 沒斜線當輸入/about看的到結果，輸入/about/ 會顯示Not Found
@app.route('/about')
def about():
return 'The about page'
好處 Reversing is often more descriptive than hard-coding the URLs. More importantly, it allows you to change URLs in one go, without having to remember to change URLs all over the place. URL building will handle escaping of special characters and Unicode data transparently for you, so you don’t have to deal with them. If your application is placed outside the URL root (say, in /myapplication instead of /), url_for() will handle that properly for you.
examples:
>>> from flask import Flask, url_for
>>> app = Flask(__name__)
>>> @app.route('/')
... def index(): pass
...
>>> @app.route('/login')
... def login(): pass
...
>>> @app.route('/user/<username>')
... def profile(username): pass
...
>>> 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')
...
/
/login
/login?next=/
/user/John%20Doe
from flask import request
@app.route('/login', methods=['GET', 'POST'])
def login():
if request.method == 'POST':
do_the_login()
else:
show_the_login_form()
To generate URLs for static files, use the special ‘static’ endpoint name: url_for(‘static’, filename=‘style.css’) The file has to be stored on the filesystem as static/style.css.
from flask import render_template
@app.route('/hello/')
@app.route('/hello/<name>')
def hello(name=None):
return render_template('hello.html', name=name)
<!doctype html>
<title>Hello from Flask</title>
{% if name %}
<h1>Hello {{ name }}!</h1>
{% else %}
<h1>Hello, World!</h1>
{% endif %}
Case 1: a module:
/application.py
/templates
/hello.html
Case 2: a package:
/application
/__init__.py
/templates
/hello.html
from flask import request
@app.route('/login', methods=['POST', 'GET'])
def login():
error = None
if request.method == 'POST':
if valid_login(request.form['username'], request.form['password']):
return log_the_user_in(request.form['username'])
else:
error = 'Invalid username/password'
# the code below is executed if the request method was GET or the credentials were invalid return render_template('login.html', error=error)
#To access parameters submitted in the URL (?key=value) you can use the args attribute:
searchword = request.args.get('key', '')
from flask import request
@app.route('/upload', methods=['GET', 'POST'])
def upload_file():
if request.method == 'POST':
f = request.files['the_file']
f.save('/var/www/uploads/uploaded_file.txt')
from flask import request
from werkzeug.utils import secure_filename
@app.route('/upload', methods=['GET', 'POST'])
def upload_file():
if request.method == 'POST':
f = request.files['the_file']
f.save('/var/www/uploads/' + secure_filename(f.filename))
from flask import request
@app.route('/')
def index():
username = request.cookies.get('username')
# use cookies.get(key) instead of cookies[key] to not get a
# KeyError if the cookie is missing.
from flask import make_response
@app.route('/')
def index():
resp = make_response(render_template(...))
resp.set_cookie('username', 'the username')
return resp
from flask import abort, redirect, url_for
@app.route('/')
def index():
return redirect(url_for('login'))
@app.route('/login')
def login():
abort(401)
this_is_never_executed()
from flask import render_template
@app.errorhandler(404)
def page_not_found(error):
return render_template('page_not_found.html'), 404
##get hold of the resulting response object inside the view use the make_response() function Imagine you have a view like this:
@app.errorhandler(404)
def not_found(error):
return render_template('error.html'), 404
You just need to wrap the return expression with make_response() and get the response object to modify it, then return it:
@app.errorhandler(404)
def not_found(error):
resp = make_response(render_template('error.html'), 404)
resp.headers['X-Something'] = 'A value'
return resp
from flask import Flask, session, redirect, url_for, escape, request
app = Flask(__name__)
@app.route('/')
def index():
if 'username' in session:
return 'Logged in as %s' % escape(session['username'])
return 'You are not logged in'
@app.route('/login', methods=['GET', 'POST'])
def login():
if request.method == 'POST':
session['username'] = request.form['username']
return redirect(url_for('index'))
return '''
<form action="" method="post">
<p><input type=text name=username>
<p><input type=submit value=Login>
</form>
'''
@app.route('/logout')
def logout():
# remove the username from the session if it's there
session.pop('username', None)
return redirect(url_for('index'))
# set the secret key. keep this really secret:
app.secret_key = 'A0Zr98j/3yX R~XHH!jmN]LWX/,?RT'
import os
os.urandom(24)
* A note on cookie-based sessions: Flask will take the values you put into the session object and serialize them into a cookie. If you are finding some values do not persist across requests, cookies are indeed enabled, and you are not getting a clear error message, check the size of the cookie in your page responses compared to the size supported by web browsers. *
* The attached logger is a standard logging Logger, so head over to the official logging documentation for more information. *
app.logger.debug('A value for debugging')
app.logger.warning('A warning occurred (%d apples)', 42)
app.logger.error('An error occurred')
from werkzeug.contrib.fixers import LighttpdCGIRootFix
app.wsgi_app = LighttpdCGIRootFix(app.wsgi_app)