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Uploaded byQiangning Hong
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Python于Web 2.0网站的应用 - QCon Beijing 2010

This document discusses Python and web frameworks. It begins with an introduction to Python and its advantages for web development. It then discusses several popular Python web frameworks including web.py, Flask, and Django. It also covers related topics like WSGI, templating with Jinja2, asynchronous programming, and deployment with virtualenv.

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Python Web 2.0 QCon Beijing 2010 http://www.flickr.com/photos/arnolouise/2986467632/
About Me • Python • 2002 Python • 2004 Python • http://www.douban.com/ people/hongqn/ • hongqn@douban.com • http://twitter.com/hongqn
Python • Python is a programming language that lets you work more quickly and integrate your systems more effectively. You can learn to use Python and see almost immediate gains in productivity and lower maintenance costs. (via http://python.org/)
Languages in C 27% Javascript 12% C++ Python 3% 58% (Pyrex/R/Erlang/Go/Shell) 1%
Why Python?
• Hello World: 1
• Hello World: 1 • :1
• Hello World: 1 • :1 • :1
• Hello World: 1 • :1 • :1 • :3
: 13
: 13 import os from collections import defaultdict d = defaultdict(int) for dirpath, dirnames, filenames in os.walk('.'): for filename in filenames: path = os.path.join(dirpath, filename) ext = os.path.splitext(filename)[1] d[ext] += len(list(open(path))) for ext, n_lines in d.items(): print ext, n_lines
• • Pythonic
• 1. svn ci 2. svn up 3. restart
• Web • • •
• Battery Included: 200+ • PyPI: 9613 packages currently • / / / / / / /... • easily extensible
Python
Python
Python Just kidding :-p
Web Server
Web Server • python -m SimpleHTTPServer
Web Server • python -m SimpleHTTPServer
web.py http://webpy.org/ import web urls = ( '/(.*)', 'hello' ) app = web.application(urls, globals()) class hello: def GET(self, name): if not name: name = 'World' return 'Hello, ' + name + '!' if __name__ == "__main__": app.run()
Flask http://flask.pocoo.org/ import flask import Flask app = Flask(__name__) @app.route("/<name>") def hello(name): if not name: name = 'World' return 'Hello, ' + name + '!' if __name__ == "__main__": app.run()
WSGI http://www.python.org/dev/peps/pep-0333/
Why so many Python web frameworks? • Because you can write your own framework in 3 hours and a total of 60 lines of Python code. • http://bitworking.org/news/ Why_so_many_Python_web_frameworks
doctest def cube(x): """ >>> cube(10) 1000 """ return x * x def _test(): import doctest doctest.testmod() if __name__ == "__main__": _test()
nose http://somethingaboutorange.com/mrl/projects/nose/ from cube import cube def test_cube(): result = cube(10) assert result == 1000
numpy http://numpy.scipy.org/ >>> from numpy import * >>> A = arange(4).reshape(2, 2) >>> A array([[0, 1], [2, 3]]) >>> dot(A, A.T) array([[ 1, 3], [ 3, 13]])
ipython http://numpy.scipy.org/ $ ipython -pylab In [1]: X = frange(0, 10, 0.1) In [2]: Y = [sin(x) for x in X] In [3]: plot(X, Y)
ipython http://numpy.scipy.org/ $ ipython -pylab In [1]: X = frange(0, 10, 0.1) In [2]: Y = [sin(x) for x in X] In [3]: plot(X, Y)
virtualenv http://virtualenv.openplans.org/ python $ python go-pylons.py --no-site-packages mydevenv $ cd mydevenv $ source bin/activate (mydevenv)$ paster create -t new9 helloworld
Pyrex/Cython cdef extern from "math.h" double sin(double) cdef double f(double x): return sin(x*x)
Pythonic
>>> import this The Zen of Python, by Tim Peters http://bit.ly/pyzencn Beautiful is better than ugly. Explicit is better than implicit. Simple is better than complex. Complex is better than complicated. Flat is better than nested. Sparse is better than dense. Readability counts. Special cases aren't special enough to break the rules.   Although practicality beats purity. Errors should never pass silently. Unless explicitly silenced.  
In the face of ambiguity, refuse the temptation to guess. There should be one-- and preferably only one --obvious way to do it. Although that way may not be Python obvious at first unless you're Dutch.   Now is better than never. Although never is often better than *right* now.   If the implementation is hard to explain, it's a bad idea. If the implementation is easy to   explain, it may be a good idea. Namespaces are one honking great idea -- let's do more of those!
Simple is better than complex class HelloWorld { public static void main(String args[]) { System.out.println("Hello World!"); } }
Simple is better than complex print "Hello World!"
Readability counts
Readability counts • {} end
Readability counts • {} end • (except "@" for decorators)
Readability counts • {} end • (except "@" for decorators) if limit is not None and len(ids)>limit: ids = random.sample(ids, limit)
TOOWTDI • There (should be) Only One Way To Do It. • vs. Perlish TIMTOWTDI (There Is More Than One Way To Do It)
TOOWTDI • There (should be) Only One Way To Do It. • vs. Perlish TIMTOWTDI (There Is More Than One Way To Do It) a = [1, 2, 3, 4, 5] b = [] for i in range(len(a)): b.append(a[i]*2)
TOOWTDI • There (should be) Only One Way To Do It. • vs. Perlish TIMTOWTDI (There Is More Than One Way To Do It) a = [1, 2, 3, 4, 5] b = [] for i in range(len(a)): b.append(a[i]*2)
TOOWTDI • There (should be) Only One Way To Do It. • vs. Perlish TIMTOWTDI (There Is More Than One Way To Do It) a = [1, 2, 3, 4, 5] b = [] b = [] for x in a: for i in range(len(a)): b.append(x*2) b.append(a[i]*2)
TOOWTDI • There (should be) Only One Way To Do It. • vs. Perlish TIMTOWTDI (There Is More Than One Way To Do It) a = [1, 2, 3, 4, 5] b = [] b = [] for x in a: for i in range(len(a)): b.append(x*2) b.append(a[i]*2)
TOOWTDI • There (should be) Only One Way To Do It. • vs. Perlish TIMTOWTDI (There Is More Than One Way To Do It) b = [x*2 for x in a]
http://twitter.com/robbinfan/status/9879724095 http://twitter.com/hongqn/status/9883515681
Python C http://www.flickr.com/photos/nicksieger/281055485/ http://www.flickr.com/photos/nicksieger/281055530/
Ruby http://www.flickr.com/photos/nicksieger/280661836/
Java http://www.flickr.com/photos/nicksieger/280662707/
Python
• svn
• svn • ( list)
• svn • ( list) • +
• svn • ( list) • + • parser
config.py MEMCACHED_ADDR = ['localhost:11211'] from local_config import *
config.py MEMCACHED_ADDR = ['localhost:11211'] from local_config import * local_config.py MEMCACHED_ADDR = [ 'frodo:11211', 'sam:11211', 'pippin:11211', 'merry:11211', ]
config.py MEMCACHED_ADDR = ['localhost:11211'] from local_config import * .py local_config.py exec MEMCACHED_ADDR = [ 'frodo:11211', 'sam:11211', 'pippin:11211', 'merry:11211', ]
•
class GroupUI(object): def new_topic(self, request): if self.group.can_post(request.user): return new_topic_ui(self.group) else: request.response.set_status(403, "Forbidden") return error_403_ui(msg=" ") def join(self, request): if self.group.can_join(request.user): ... class Group(object): def can_post(self, user): return self.group.has_member(user) def can_join(self, user): return not self.group.has_banned(user)
class GroupUI(object): @check_permission('post', msg=" ") def new_topic(self, request): return new_topic_ui(self.group) @check_permission('join', msg=" ") def join(self, request): ... class Group(object): def can_post(self, user): return self.group.has_member(user) def can_join(self, user): return not self.group.has_banned(user)
decorator def print_before_exec(func): def _(*args, **kwargs): print "decorated" return func(*args, **kwargs) return _ @print_before_exec def double(x): print x*2 double(10)
decorator def print_before_exec(func): def _(*args, **kwargs): print "decorated" return func(*args, **kwargs) return _ decorated @print_before_exec def double(x): 20 print x*2 double(10)
class check_permission(object): def __init__(self, action, msg=None): self.action = action self.msg = msg def __call__(self, func): def _(ui, req, *args, **kwargs): f = getattr(ui.perm_obj, 'can_' + self.action) if f(req.user): return func(ui, *args, **kwargs) raise BadPermission(ui.perm_obj, self.action, self.msg) return _
class check_permission(object): def __init__(self, action, msg=None): self.action = action self.msg = msg def __call__(self, func): def _(ui, req, *args, **kwargs): f = getattr(ui.perm_obj, 'can_' + self.action) if f(req.user): return func(ui, *args, **kwargs) raise BadPermission(ui.perm_obj, self.action, self.msg) return _
class check_permission(object): def __init__(self, action, msg=None): self.action = action self.msg = msg def __call__(self, func): def _(ui, req, *args, **kwargs): f = getattr(ui.perm_obj, 'can_' + self.action) if f(req.user): return func(ui, *args, **kwargs) raise BadPermission(ui.perm_obj, self.action, self.msg) return _
class check_permission(object): def __init__(self, action, msg=None): self.action = action self.msg = msg def __call__(self, func): def _(ui, req, *args, **kwargs): f = getattr(ui.perm_obj, 'can_' + self.action) if f(req.user): return func(ui, *args, **kwargs) raise BadPermission(ui.perm_obj, self.action, self.msg) return _
class check_permission(object): def __init__(self, action, msg=None): self.action = action self.msg = msg def __call__(self, func): def _(ui, req, *args, **kwargs): f = getattr(ui.perm_obj, 'can_' + self.action) if f(req.user): return func(ui, *args, **kwargs) raise BadPermission(ui.perm_obj, self.action, self.msg) return _
class check_permission(object): def __init__(self, action, msg=None): self.action = action self.msg = msg def __call__(self, func): def _(ui, req, *args, **kwargs): f = getattr(ui.perm_obj, 'can_' + self.action) if f(req.user): return func(ui, *args, **kwargs) raise BadPermission(ui.perm_obj, self.action, self.msg) return _
class GroupUI(object): @check_permission('post', msg=" ") def new_topic(self, request): return new_topic_ui(self.group) @check_permission('join', msg=" ") def join(self, request): ... class Group(object): def can_post(self, user): return self.group.has_member(user) def can_join(self, user): return not self.group.has_banned(user)
•
def send_notification_mail(email, subject, body): msg = MSG_SEND_MAIL + '0' + email + '0' + subject + '0' + body mq.put(msg) def async_worker(): msg = mq.get() msg = msg.split('0') cmd = msg[0] if cmd == MSG_SEND_MAIL: email, subject, body = msg[1:] fromaddr = 'no-reply@douban.com' email_body = make_email_body(fromaddr, email, subject, body) smtp = smtplib.SMTP('mail') smtp.sendmail(fromaddr, email, email_body) elif cmd == MSG_xxxx: ... elif cmd == MSG_yyyy: ...
@async def send_notification_mail(email, subject, body): fromaddr = 'no-reply@douban.com' email_body = make_email_body(fromaddr, email, subject, body) smtp = smtplib.SMTP('mail') smtp.sendmail(fromaddr, email, email_body)
def async(func): mod = sys.modules[func.__module__] fname = 'origin_' + func.__name__ mod.__dict__[fname] = func def _(*a, **kw): body = cPickle.dumps((mod.__name__, fname, a, kw)) mq.put(body) return _ def async_worker(): modname, fname, a, kw = cPickle.loads(mq.get()) __import__(modname) mod = sys.modules[modname] mod.__dict__[fname](*a, **kw)
def async(func): mod = sys.modules[func.__module__] fname = 'origin_' + func.__name__ mod.__dict__[fname] = func def _(*a, **kw): body = cPickle.dumps((mod.__name__, fname, a, kw)) mq.put(body) return _ def async_worker(): modname, fname, a, kw = cPickle.loads(mq.get()) __import__(modname) mod = sys.modules[modname] mod.__dict__[fname](*a, **kw)
def async(func): mod = sys.modules[func.__module__] fname = 'origin_' + func.__name__ mod.__dict__[fname] = func def _(*a, **kw): body = cPickle.dumps((mod.__name__, fname, a, kw)) mq.put(body) return _ def async_worker(): modname, fname, a, kw = cPickle.loads(mq.get()) __import__(modname) mod = sys.modules[modname] mod.__dict__[fname](*a, **kw)
def async(func): mod = sys.modules[func.__module__] fname = 'origin_' + func.__name__ mod.__dict__[fname] = func def _(*a, **kw): body = cPickle.dumps((mod.__name__, fname, a, kw)) mq.put(body) return _ def async_worker(): modname, fname, a, kw = cPickle.loads(mq.get()) __import__(modname) mod = sys.modules[modname] mod.__dict__[fname](*a, **kw)
def async(func): mod = sys.modules[func.__module__] fname = 'origin_' + func.__name__ mod.__dict__[fname] = func def _(*a, **kw): body = cPickle.dumps((mod.__name__, fname, a, kw)) mq.put(body) return _ def async_worker(): modname, fname, a, kw = cPickle.loads(mq.get()) __import__(modname) mod = sys.modules[modname] mod.__dict__[fname](*a, **kw)
def async(func): mod = sys.modules[func.__module__] fname = 'origin_' + func.__name__ mod.__dict__[fname] = func def _(*a, **kw): body = cPickle.dumps((mod.__name__, fname, a, kw)) mq.put(body) return _ def async_worker(): modname, fname, a, kw = cPickle.loads(mq.get()) __import__(modname) mod = sys.modules[modname] mod.__dict__[fname](*a, **kw)
def async(func): mod = sys.modules[func.__module__] fname = 'origin_' + func.__name__ mod.__dict__[fname] = func def _(*a, **kw): body = cPickle.dumps((mod.__name__, fname, a, kw)) mq.put(body) return _ def async_worker(): modname, fname, a, kw = cPickle.loads(mq.get()) __import__(modname) mod = sys.modules[modname] mod.__dict__[fname](*a, **kw)
def async(func): mod = sys.modules[func.__module__] fname = 'origin_' + func.__name__ mod.__dict__[fname] = func def _(*a, **kw): body = cPickle.dumps((mod.__name__, fname, a, kw)) mq.put(body) return _ def async_worker(): modname, fname, a, kw = cPickle.loads(mq.get()) __import__(modname) mod = sys.modules[modname] mod.__dict__[fname](*a, **kw)
• cache (SQL, , etc)
def get_latest_review_id(): review_id = mc.get('latest_review_id') if review_id is None: review_id = exc_sql("select max(id) from review") mc.set('latest_review_id', review_id) return review_id
@cache('latest_review_id') def get_latest_review_id(): return exc_sql("select max(id) from review")
def cache(key): def deco(func): def _(*args, **kwargs): r = mc.get(key) if r is None: r = func(*args, **kwargs) mc.set(key, r) return r return _ return deco
def cache(key): def deco(func): def _(*args, **kwargs): r = mc.get(key) if r is None: r = func(*args, **kwargs) mc.set(key, r) return r return _ return deco
cache key def get_review(id): key = 'review:%s' % id review = mc.get(key) if review is None: # cache miss id, author_id, text = exc_sql("select id, author_id, text from review where id=%s", id) review = Review(id, author_id, text) mc.set(key, review) return review
cache key decorator @cache('review:{id}') def get_review(id): id, author_id, text = exc_sql("select id, author_id, text from review where id=%s", id) return Review(id, author_id, text)
def cache(key_pattern, expire=0): def deco(f): arg_names, varargs, varkw, defaults = inspect.getargspec(f) if varargs or varkw: raise Exception("not support varargs") gen_key = gen_key_factory(key_pattern, arg_names, defaults) def _(*a, **kw): key = gen_key(*a, **kw) r = mc.get(key) if r is None: r = f(*a, **kw) mc.set(key, r, expire) return r return _ return deco
def cache(key_pattern, expire=0): def deco(f): arg_names, varargs, varkw, defaults = inspect.getargspec(f) if varargs or varkw: raise Exception("not support varargs") gen_key = gen_key_factory(key_pattern, arg_names, defaults) def _(*a, **kw): key = gen_key(*a, **kw) r = mc.get(key) if r is None: r = f(*a, **kw) mc.set(key, r, expire) return r return _ return deco
def cache(key_pattern, expire=0): def deco(f): arg_names, varargs, varkw, defaults = inspect.getargspec(f) if varargs or varkw: raise Exception("not support varargs") gen_key = gen_key_factory(key_pattern, arg_names, defaults) def _(*a, **kw): key = gen_key(*a, **kw) r = mc.get(key) if r is None: r = f(*a, **kw) mc.set(key, r, expire) return r return _ return deco
inspect.getargspec >>> import inspect >>> def f(a, b=1, c=2): ... pass ... >>> inspect.getargspec(f) ArgSpec(args=['a', 'b', 'c'], varargs=None, keywords=None, defaults=(1, 2)) >>> >>> >>> def f(a, b=1, c=2, *args, **kwargs): ... pass ... >>> inspect.getargspec(f) ArgSpec(args=['a', 'b', 'c'], varargs='args', keywords='kwargs', defaults=(1, 2))
def cache(key_pattern, expire=0): def deco(f): arg_names, varargs, varkw, defaults = inspect.getargspec(f) if varargs or varkw: raise Exception("not support varargs") gen_key = gen_key_factory(key_pattern, arg_names, defaults) def _(*a, **kw): key = gen_key(*a, **kw) r = mc.get(key) if r is None: r = f(*a, **kw) mc.set(key, r, expire) return r return _ return deco
def cache(key_pattern, expire=0): def deco(f): arg_names, varargs, varkw, defaults = inspect.getargspec(f) if varargs or varkw: raise Exception("not support varargs") gen_key = gen_key_factory(key_pattern, arg_names, defaults) def _(*a, **kw): key = gen_key(*a, **kw) r = mc.get(key) if r is None: hint: r = f(*a, **kw) mc.set(key, r, expire) return r • str.format in python 2.6: '{id}'.format(id=1) => '1' return _ return deco • dict(zip(['a', 'b', 'c'], [1, 2, 3])) => {'a': 1, 'b': 2, 'c': 3}
def cache(key_pattern, expire=0): def deco(f): arg_names, varargs, varkw, defaults = inspect.getargspec(f) if varargs or varkw: raise Exception("not support varargs") gen_key = gen_key_factory(key_pattern, arg_names, defaults) def _(*a, **kw): key = gen_key(*a, **kw) r = mc.get(key) if r is None: hint: r = f(*a, **kw) mc.set(key, r, expire) return r • str.format in python 2.6: '{id}'.format(id=1) => '1' return _ return deco • dict(zip(['a', 'b', 'c'], [1, 2, 3])) => {'a': 1, 'b': 2, 'c': 3}