Wednesday, December 10, 2008

Save CPU Usage! Dont Use StringIO

After enabling the python profiler, I noticed that StringIO adds about 500 CPU usage to your process so ignoring the use of it will save a bit of cpu usage.

Monday, November 10, 2008

Custom Python Decorator

Decorators allow developers to use aspect oriented approach. Here is an example of a custom python/django decorator that checks if the user is a super user and redirects it to login page if not

def super_user(func):
    def call(request, *args, **kwds):
        user = request.user
        if user.is_authenticated() and user.is_superuser:
            return func(request, *args, **kwds)
        else:
            return utils.redirect(settings.LOGIN_URL)
    return call

@super_user
def my_view(request):
    pass

Saturday, November 08, 2008

Django Tip: Cache List instead of QuerySet to minimize queries to the database

While playing with django debug toolbar, I noticed that some page on my application causes serious amount of queries that is being executed. One page actually executes around 580 queries so I investigated and noticed that this was caused probably by lazy initialization, not using select_related() on my queries and i'm caching QuerySet object instead of list.

An example of a getter function on my model:

@property
    def data(self):
        cache_data = getattr(self, 'cache_data', None)
        if cache_data:
            return cache_data
        else:
            self.cache_data = TimecardData.objects.filter(timecard_day=self)
            return self.cache_data

@property
    def data(self):
        cache_data = getattr(self, 'cache_data', None)
        if cache_data:
            return cache_data
        else:
            self.cache_data = list(TimecardData.objects.select_related()
.filter(timecard_day=self))
            return self.cache_data

@property
    def data(self):
        cache_data = getattr(self, 'cache_data', None)
        if cache_data != None:
            return cache_data
        else:
            self.cache_data = list(TimecardData.objects.select_related().filter(timecard_day=self))
            return self.cache_data

Tuesday, November 04, 2008

Python 2.5 Date/Time Module Poorly Designed?

I'm not sure If I'm the only one who feel that the date/time module in python 2.5 is very hard to use. If any of you ever tried using joda time, you'll notice that it's way to easy compared to python's date/time library.

Correct me If i'm wrong but joda time was created by Google guys so I hope that in the near future, python will have a better date/time library (since Google is the main supporter of python).

Saturday, October 18, 2008

Host Python Applications Better With mod_wsgi

As I was browsing, I came across an article used to host python web applications better. The module called 'mod_wsgi' is a new&better apache module than mod_python when hosting django/python apps. I haven't personally tried it (maybe I will this coming weekend) but the comments by other people are very interesting. Anyway to give you some short round-up, this are the things that it can do:

• Can serve dynamic content by about 100-150% faster compare to mod_python
• Consumes less memory
• Secure (Don't know yet why it's secure)

Links:

http://code.google.com/p/modwsgi/

http://www.technobabble.dk/2008/aug/25/django-mod-wsgi-perfect-match/

http://code.djangoproject.com/wiki/django_apache_and_mod_wsgi