обзор Python

Python for Web
by Alex Radchenko and Yegor Nazarkin,
www.mediasapiens.co

twitter: @dixon_che, @nimnull

Who we are?
Web solutions

Flexible
Pythonic
Development
Neat OpenSource
E-commerce
Mobile

Why .py?
Conception suddenly changed!

Why .py?
Or in JAVA world tones of X
ML
ads
hre g
h of t izin
ell on
syn chr

modules ning
repo? ve rsio
l ibra ries
no

Why .py?
A bit of PHP? Built-in and library APIs are
a
disorganized mess
c ti ons
S QL inje
core bugs

not transitive

silent e rrors

Why .py?
Python is a very new language; in fact it was released by its
designer, Guido Van Rossum, in February 1991 while working
for CWI also known as Stichting Mathematisch Centrum.

•Interpreted, interactive, object-oriented
•It incorporates modules, exceptions, dynamic data types
and classes.
•Extensible in C or C++.
•Portable across all major hardware and software platforms.

Why .py?
Zen
Language designed for readability and productivity of the
end-up developer

Modules
http://pypi.python.org

Huge community
https://github.com/languages/Python

Why .py? Explicit is better than implicit.
Beautiful is better than ugly.
Flat is better than nested.
Readability counts.

class Mediator(object):
def __init__(self):
self.signals = {}

def signal(self, signal_name, *args, **kwargs):
for handler in self.signals.get(signal_name, []):
handler(*args, **kwargs)

def connect(self, signal_name, receiver):
handlers = self.signals.setdefault(signal_name, [])
handlers.append(receiver)

def disconnect(self, signal_name, receiver):
self.signals[signal_name].remove(receiver)

The Zen of Python

Why .py? Explicit is better than implicit?
Beautiful is better than ugly?
Flat is better than nested?
class Mediator {
private boolean slotFull = false;
private int number;
Readability counts?
public synchronized void storeMessage(int num) {
while (slotFull == true) {
try {
wait();
}
catch (InterruptedException e) { }
}
slotFull = true;
number = num;
notifyAll();
}
public synchronized int retrieveMessage() {
// no message to retrieve
while (slotFull == false)
try {
wait();
}
catch (InterruptedException e) { }
slotFull = false;
notifyAll();
return number;
}
}

Does the Java have a Zen?

Why .py?
Good old spaghetti async style
init: function(msg, obj) {
chrome.pageAction.show(tabId);
me.api.authorize(function() {
me.api.checkDoc(msg.doc,
function(data) {
obj.get(msg);
me.api.realtime.getUpdates({
tabId: tabId,
ids: [msg.doc.id],
callbackOk: function(data) {
if (data.event == 'connected') {
obj.get(msg);
}
port.postMessage({_action: 'update', data: data});
},
callbackError: function(data) {
obj.get(msg);
}
});
},
function(data) {
console.warn('Bad document', data.responseText);
}
);
});
},

Why .py?
And how we see the same things
@tornado.web.asynchronous
@gen.engine
def get(self, user_id=None):
if user_id is not None:
user = yield gen.Task(User.get, user_id)
self.set_secure_cookie('uid', unicode(user._id))
response = user.as_dict()
else:
count = yield gen.Task(User.objects.count)
if not count:
yield gen.Task(User.create({'nickname': "John Doe"}).save)
users = yield gen.Task(User.objects.find, None)
response = [u.as_dict() for u in users]
self.write(json_encode(response))
self.finish()

Why .py? Need functional?

stripped_list = [line.strip() for line in line_list
List comprehensions if line != ""]

Generators def generate_ints(N):
for i in range(N):
yield i

val = (yield i)

Built-ins map(upper, ['sentence', 'fragment'])

[upper(s) for s in ['sentence', 'fragment']]

filter(is_even, range(10))

[x for x in range(10) if is_even(x)]

total = reduce(lambda a, b: (0, a[1] + b[1]), items)[1]

Why .py? Decorators

from functools import wraps

def my_decorator(func):

@wraps(func)
def wrapper(*args, **kwargs):
# we can do smth with arguments
print “args:”, args
response = func(*args, **kwargs)
# end with the method result too
return wrapper

@my_decorator
def func1(arg1):
return "inside func1()", arg1

>>>print func1(‘test’)

“args: [‘test’]”
“inside func1() test”

Why .py? Descriptor’s magic

An object attribute with "binding behavior", one whose
attribute access has been overridden by methods in the
descriptor protocol.
class RevealAccess(object):

def __init__(self, initval=None, name='var'):
self.val = initval
self.name = name

def __get__(self, obj, objtype):
print 'Retrieving', self.name
return self.val

def __set__(self, obj, val):
print 'Updating' , self.name
self.val = val

class MyClass(object):
x = RevealAccess(10, 'var "x"')
y = 5

>>> m = MyClass()
>>> m.x
Retrieving var "x"
10

Why .py? Metaclasses

Metaclasses are deeper magic than 99% of users should
ever worry about. If you wonder whether you need them,
you don't (the people who actually need them know with
certainty that they need them, and don't need an
explanation about why)
Tim Peters

class Singleton(type):
instance = None
def __call__(cls, *args, **kw):
if cls.instance is None:
cls.instance = super(Singleton, cls).__call__(*args, **kw)
return cls.instance

class Foo(object):
__metaclass__ = Singleton

Why .py? Need an IDE?

Convenient way: Hacker’s choices are:
PyCharm VIM
NinjaIDE Emacs
WingIDE

Hipster’s choice:
Sublime Text (written in python, actually)

Why .py?

But the C is much more faster!

Why .py?

Stop! The main problem sounds like:
the development speed,
developer’s motivation

Have we just mentioned that the most critical parts could be written in C/C++?

The Web in the details
Fast prototyping

OMG! WTF? It handles loading!

The Freedom of Choice:

• General approach on request/response processing
• Reusable modules/parts
• Template engines
• ORM (RDBMS, noSQL)
• Caching backends
• Messages queue APIs (ZMQ, RabbitMQ)
• Localization out of the box
• Great documentation! Testing frameworks
• Debugging and profiling

Batteries:

nimnull@fox-laptop:~$ easy_install <battery name>

Logic-less templates:

• Django Template Engine
• Tornado Template Engine
• Jinja2
• Mako
• Genshi

• Inheritance
• Extending
• Compiled to the Python

DB storage backends:

• General approach of DBAPI for RDBMS
• Arguments escaping, type checks
• noSQL (if you expect it)

• SQLAlchemy (postgres, mysql, oracle, mssql)
• MongoKit
• Mongoengine
• CouchDbKit

Asynchronous:

• Tornado
• twisted.web
• gevent

• epoll (linux), kqueue (BSD)
• Spaghetti? No Way! (Promise/Deffered)

Success story, bro
Pinterest Disqus Quora

Spotify Instagram Bitbucket

OpenStack
FriendFeed
Dropbox

UA Community
http://citypy.org/ http://ua.pycon.org/

Kyiv
Kharkiv
Lviv
Donetsk
Odessa (py.drinkups)

обзор Python

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