Articles Tagged python2.x

Python tips & tricks

Base python tips & tricks

Recently i've read the book Learning Python, 5th Edition by Mark Lutz. Here is a list of most interesting insights for me.

  • set generation:

    {x for x in [1,2]}
    set(x for x in [1,2])
    assert set(x for x in [1,2]) == {x for x in [1,2]}
    
  • dict generation:

    {x:x**2 for x in [1,2]}
    dict((x, x**2) for x in [1,2])
    assert {x:x**2 ...

Posted on 2015-04-30

Python logging for every day

When writing a small python program or script, it is sometimes needed to output debug message or maybe event. It is known, that python has logging module exactly for that purpose. But in my case usually such thing happens: it is lack of time and hands just writes print instead of logging, because i can't remember all those complicated logging settings. But then, if script is launched often or i must provide it ...

Posted on 2013-08-20

Unicode string formatting

Did you know, if one of values in string formatting expression with % operator is unicode, then result string will also be unicode?

>>> "Hello, %s" % u"Alex"
u'Hello, Alex'
>>> "Hello, %s" % u"Алексей"
u'Hello, \u0410\u043b\u0435\u043a\u0441\u0435\u0439'

I used to work with .format string method and its behavior is more attractive to me: type of source string is saved and if some parameter contains non-ascii symbols, UnicodeEncodeError exception is raised ...

Posted on 2013-06-20

Parse url which contains unicode query, using urlparse.parse_qs

Task: get dictionary of URL GET query. For example, we have following url:

http://example.com/?key=value&a=b

it is needed to get a dict:

{'key': ['value'], 'a': ['b']}

Values are lists, because one key may have several values:

In: http://example.com/?key=value&a=b&a=c
Out: {'key': ['value'], 'a': ['b', 'c']}

In python there is a function urlparse.parse_qs for that purpose:

>>> import urlparse
>>> query = "key=value&a=b ...

Posted on 2013-05-22

Python function with mutable default arguments

Python mutable default arguments

In python default function arguments are created during executing instruction def and not at each function call. If argument value is immutable object (for example string, integer, tuple) it is ok, but if value is mutable, then there can be a trap:

    def foo(l=[]):
        l.append('x')
        return l

It seems, that every call to foo() will return list ['x']. But:

    >>> foo()
    ['x']
    >>> foo()
    ['x', 'x']
    >>> foo()
    ['x', 'x', 'x']

So, if it is ...

Posted on 2013-03-06

Script for downloading music from vkontakte

Vkontakte audio download

A quick search of corresponding python script doesn't give results. In post on habra link is broken. So i decided to write my own bicycle, it is avaliable here.

Launch (needs installed python interpreter):

python vkcom_audio_download.py

Tested on python 2.6 and 2.7. No external libraries required.

Algorithm:

Script checks saved access_token. If it doesn't exists or expired, then page with authorisation is opened in browser. After confirmation you will ...

Posted on 2013-02-04

MobileESP: Easily detect mobile web site visitors

Script will be useful, if you want to show different version of site for desktop computers and mobile devices. Big variety of methods to detect mobile type. Avaliable in different languages, including python. The port to python was made by me with help from my freelance customer.

Here how it can be used in django project:

from mobileesp import mdetect

user_agent = request.META.get("HTTP_USER_AGENT")
http_accept = request.META.get("HTTP_ACCEPT")
if user_agent and http_accept:
    agent ...

Posted on 2012-11-29

Debug django project with embedded python debugger pdb

I use sublime-text as code editor. It doesn't have a debugger, so to debug django projects i often used

print var_name

and look for output in local development server console. I use this approach today also, but sometimes it is great to run code step by step to see variables at each step.

It can be done with embedded python debugger pdb:

import pdb; pdb.set_trace()

I.e. we put this line in needed ...

Posted on 2012-11-18

Cloud service Openshift

Openshift logo

I know a few hosting providers with free account and python availability. It is Google App Engine and Alwaysdata. But recently i found great project Openshift from RedHat and this blog site is working on it. Let me describe mentioned hostings first.

Google app engine

The main trouble of google app engine - limited amount of python libraries. Of course, you can use pure python libs, but you can't setup libs that requires C compilation ...

Posted on 2012-10-08

This site

Features:

Often reading other blogs i had a wish to start my own, but i just can't find time for it. Also i was wondering, what will i write ...

Posted on 2012-08-28