amix.dk blog

Displaying timezones better in Python

Sat, 05 May 2012 17:04:16 GMT

I have released timezones for Python, it makes timezones more user-friendly for the users by formatting timezones better and auto-guessing timezone based on the user's IP address.

You can:

Install the library via sudo pip install timezones
Read the documentation
Fork the code on github

The library provides:

User friendly rendering of common timezones. pytz.common_timezones includes 430 common timezones, without any smart sorting or display of useful information such as timezone offsets. This provides an awful experience if you just present this to the users - - like it's done in Django
Auto-guessing a user's timezone based on the user's IP. This is done via pygeoip
Supporting fixed offsets timezones, such as "GMT +1:00"

Example usage of the library:

from timezones.tz_rendering import html_render_timezones

html_timezones = html_render_timezones(select_name=timezone',
                                       current_selected=current_timezone,
                                       user_ip=get_current_ip(),
                                       first_entry=_('Select your timezone'))

A screenshot of the library in use [in Wedoist]:

Updating caching headers for Amazon S3 and CloudFront

Wed, 02 May 2012 17:20:29 GMT

I made a major blunder when setting caching headers for Amazon S3 and CloudFront. Making such a blunder makes my sites slower and costs more in bandwidth. In this little blog post I will detail how to fix this and make sure you use correct caching headers.

Use the correct syntax

The first rule, make sure that the syntax is correct. Correct syntax looks like this:

Cache-Control: max-age=155520000, public
Expires: Sat, 29 Apr 2017 13:31:45-0000 GMT

For me, I used following syntax (it's wrong and wont be understood by browsers!):

Cache-Control: max-age 155520000

Read more in RFC 2616 for all the details sounding headers.

Be greedy and use file versioning

Use file versioning (for example make md5 hash a part of the name). You are forced to do this anyway since CloudFront does not support invalidations that well.

Already using file versioning? Great, then set your expires a lot of years in the future, since the filename will change when the files changes (i.e. you don't have to worry about invalidating old files).

Made a blunder? Use my script to update all S3 files in a bucket

Before you update headers to every S3 object make sure that the code works by testing it on dummy objects. I had a lot of issues getting it to work, since it will replace older metadata and not just update it. You can use my script (but it's not bulletproof, so be sure that any missing headers that you use are copied over to the updated metadata).

You will need to do following:

Using the script below test it out on dummy S3 objects
Update headers for every S3 object
Create new Amazon CloudFront distributions after the S3 objects are updated. Can be done via aws.amazon.com
Update DNS records to use the new distributions

#!/usr/bin/env python
"""
    fix_s3_cache_headers
    ~~~~~~~~

    Updates S3 objects with new cache-control headers.

    Usage::
        python fix_cloudfront.py <bucket_name> <keys>*

    Examples::
        Updates all keys of avatars.wedoist.com bucket::
            python fix_cloudfront.py avatars.wedoist.com

        Updates only one key::
            python fix_cloudfront.py avatars.w.com d39c2.gif

    Read more here::
        http://amix.dk/blog/post/19687

    :copyright: by Amir Salihefendic ( http://amix.dk/ )
    :license: MIT
"""
import sys
import mimetypes
import email
import time
import types
from datetime import datetime, timedelta

from boto.s3.connection import S3Connection
from boto.cloudfront import CloudFrontConnection


#--- AWS credentials ----------------------------------------------
AWS_KEY = '...'
AWS_SECRET = '...'


#--- Main function ----------------------------------------------
def main(s3_bucket_name, keys=None):
    s3_conn = S3Connection(AWS_KEY, AWS_SECRET)

    bucket = s3_conn.get_bucket(s3_bucket_name)

    if not keys:
        keys = bucket.list()

    for key in keys:
        if type(key) == types.StringType:
            key_name = key
            key = bucket.get_key(key)
            if not key:
                print 'Key not found %s' % key_name
                continue

        # Force a fetch to get metadata
        # see this why: http://goo.gl/nLWt9
        key = bucket.get_key(key.name)

        aggressive_headers = _get_aggressive_cache_headers(key)
        key.copy(s3_bucket_name, key, metadata=aggressive_headers, preserve_acl=True)

        print 'Updated headers for %s' % key.name


#--- Helpers ----------------------------------------------
def _get_aggressive_cache_headers(key):
    metadata = key.metadata

    metadata['Content-Type'] = key.content_type

    # HTTP/1.0 (5 years)
    metadata['Expires'] = '%s GMT' %\
        (email.Utils.formatdate(
            time.mktime((datetime.now() +
            timedelta(days=365*5)).timetuple())))

    # HTTP/1.1 (5 years)
    metadata['Cache-Control'] = 'max-age=%d, public' % (3600 * 24 * 360 * 5)

    return metadata


if __name__ == '__main__':
    main( sys.argv[1],
          sys.argv[2:] )

Product features vs. UI elements on the screen

Sat, 28 Apr 2012 20:17:53 GMT

Like noted in The essence of minimal product design successful products hide complexity from the users. Balsamiq has a great graph illustrating this as well.

from The Balsamiq Mockups Manifesto

A man is a success

Mon, 23 Apr 2012 15:44:48 GMT

Original image

Hiring talented iOS and Android developers

Thu, 15 Mar 2012 12:20:52 GMT

We are expanding the team at Todoist and Wedoist with iOS and Android programmers.

Some of our stats:

Over 300.000 users
Rapid growth
Our business is profitable
We started fulltime with the company just 8 months ago. Imagine the future :-)

Join us either freelance or full-time and work on something that makes the world more productive.

Send your resume to amix@amix.dk, be sure to include some code you are proud of (or a link to your GitHub/BitBucket profile).

Open sourced coffee-watcher, less-watcher and watcher_lib

Wed, 22 Feb 2012 15:25:19 GMT

I have updated/published following libraries today:

coffee-watcher: a script that can watch a directory and recompile your .coffee scripts if they change
less-watcher: a script that can watch a directory and recompile your .less scripts if they change
watcher_lib: A library that can watch a directory and recompile files if they change. Can be used to build watcher scripts

Basically these scripts are useful for development as you don't need to think about recompiling your files. You can also use watcher_lib to implement custom watchers.

coffee-watcher

Documentation

sudo npm install coffee-watcher

coffee-watcher -p [prefix] -d [directory]

Options:
  -d  Specify which directory to scan.
  -p  Which prefix should the compiled files have?
      Default is style.coffee will be compiled to .coffee.style.css
  -h  Prints help

less-watcher

Documentation

sudo npm install less-watcher

less-watcher -p [prefix] -d [directory]

Options:
  -d  Specify which directory to scan.
  -p  Which prefix should the compiled files have?
      Default is style.less will be compiled to .less.style.css
  -h  Prints help

watcher_lib

Documentation

sudo npm install watcher_lib

How to build a generic watcher (here is less-watcher's implementation):

# Use `watcher-lib`, a library that abstracts away most of the implementation details.
watcher_lib = require 'watcher_lib'

# Searches through a directory structure for *.less files using `find`.
# For each .less file it runs `compileIfNeeded` to compile the file if it's modified.
findLessFiles = (dir) ->
    watcher_lib.findFiles('*.less', dir, compileIfNeeded)

# Keeps a track of modified times for .less files in a in-memory object,
# if a .less file is modified it recompiles it using compileLessScript.
#
# When starting the script all files will be recompiled.
WATCHED_FILES = {}
compileIfNeeded = (file) ->
    watcher_lib.compileIfNeeded(WATCHED_FILES, file, compileLessScript)

# Compiles a file using `lessc`. Compilation errors are printed out to stdout.
compileLessScript = (file) ->
    fnGetOutputFile = (file) -> file.replace(/([^\/\\]+)\.less/, "#{argv.p}$1.css")
    watcher_lib.compileFile("lessc #{ file }", file, fnGetOutputFile)

# Starts a poller that polls each second in a directory that's
# either by default the current working directory 
# or a directory that's passed through process arguments.
watcher_lib.startDirectoryPoll(argv.d, findLessFiles)

css_image_concat: Improve performance by concating your images

Mon, 20 Feb 2012 15:58:32 GMT

I have updated my CSS image contact script from 2007. This script can concat images into one image and create a CSS file with classes. This is a super useful optimization when you want decrease issuing a lot of HTTP requests due to a lot of small images (like icons).

What is the idea behind this?

The idea is to take all separated images and concat them to one image file:

This means that only one HTTP request is made to fetch all the images.

CSS is then used to display an image (by using background offsets):

.cmp_email_icon {
    background: transparent url(all_images.gif) 0 -48px no-repeat;
    width: 21px;
    height: 16px;
}

Installing it

sudo pip install css_image_concat

This script also requires ImageMagick.

Using it

$ css_image_concat static/icons static/all_icons.png static/all_icons.css
Parsed 18 in static/icons
Written CSS file: static/all_icons.css
Written image file: static/all_icons.png
----

GitHub and PyPi

You can checkout the code from here:

Focusing is about saying no - Steve Jobs (WWDC'97)

Mon, 20 Feb 2012 14:02:23 GMT

When Steve Jobs returned back to Apple in 1997 he fired thousands of people and discontinued lots of projects. In WWDC'97 he explained why:

Apple suffered for several years from lousy engineering management. There were people that were going off in 18 different directions... What happened was that you looked at the farm that's been created with all these different animals going in all different directions, and it doesn't add up - the total is less than the sum of the parts. We had to decide: What are the fundamental directions we are going in? What makes sense and what doesn't? And there were a bunch of things that didn't.

Focusing is saying yes, right? No. Focusing is about saying no. You've got to say, no, no, no. The result of that focus is going to be some really great products where the total is much greater than the sum of the parts.

Niall Ferguson: The 6 killer apps of prosperity

Tue, 14 Feb 2012 08:47:10 GMT

I would recommend watching this TED talk: Niall Ferguson: The 6 killer apps of prosperity

Over the past few centuries, Western cultures have been very good at creating general prosperity for themselves. Historian Niall Ferguson asks: Why the West, and less so the rest? He suggests half a dozen big ideas from Western culture -- call them the 6 killer apps -- that promote wealth, stability and innovation. And in this new century, he says, these apps are all shareable.

The course of the Empire

Interview with DoesWhat.com

Fri, 10 Feb 2012 08:42:50 GMT

I gave a short interview to DoesWhat.com. You can read it here:

Interview with Amir Salihefendic

What are you most excited about at the moment?
I want to make the world more productive. I wake up each morning and I am excited to work towards this goal.