Parse any number string to float

function stringToFloat(str) {
    var fractional_part, integer, fractional = "", found = false, i;
    // remove leading and trailing non-digit symbols
    str = str.replace(/[^\d,\.]+$/, '').replace(/^[^\d,\.]+/, '');
    fractional_part = str.slice(-3);
    for (i = fractional_part.length - 1; i >= 0; i--) {
        if (/\d/.test(fractional_part[i])) {
            fractional = fractional_part[i] + fractional;
        } else {
            found = true;
            break;
        }
    }
    if (fractional && found) {
        integer = str.slice(0, i - 3);
    } else {
        integer = str;
        fractional = "";
    }
    return parseFloat(integer.replace(/[^\d]/g, '') + "." + fractional);
}

Delete tags

To delete tags in git that match some regex, both locally and remotely, I use these two commands

# remove tags on origin
git ls-remote --tags  | awk '/tags\/release.*[^\}]$/ {print ":" $2}' | xargs git push origin

# remove locally
git tag -l | awk '/^release.*$/ {print $1}' | xargs git tag -d

Increase trackpad speed beyond system settings

If you are not satisfied with your trackpad speed and you've already set it to the maximum in System Settings pane, it could help you.

Go to Terminal and

open ~/Library/Preferences/.GlobalPreferences.plist

You need com.apple.trackpad.scaling. System Preferencies's maximum is 3. From my experience, 30 is insane. I use 15, it's enough to move cursor with one movement from the left side of left screen the right of the right one.

Showing an image when dragging any tag in HTML

Chrome and Safari support displaying a ghost image for draggable objects out of the box, Firefox does not. It's not a big deal, I'd say a matter of one event handler.

This is a sample HTML:

Drag Me!

and JavaScript code:

$(function () {
    var dragImage = document.createElement("img");
    dragImage.src = "/image/to/show/when/dragging.jpg";
    function handleDragStart(e) {
        e.dataTransfer.effectAllowed = 'move';
        e.dataTransfer.setDragImage(dragImage, e.layerX, e.layerY);
    }

    $("#draggableObject").get(0).addEventListener('dragstart', handleDragStart, false);
});

Native HTML5 Drag and Drop

MDN::dataTransfer

Line numbers in Vim

I would like to cover all aspects known for me related to the line numbers in Vim.

Command	Description
:0	move cursor to the first
:42 42gg 42G	move cursor to 42nd
:G	move cursor to the last

Show line numbers in current file

:set number

Hide line numbers in current file

:set nonumber

Computed field on TabularInline (StackedInline)

Django admin doesn't provide list_display attribute on its inline admin classes. That's right, since the only supposed view for those classes is editable form. So, to display a result of custom function's call, it needs to add the name of the function (that can be declared either on the admin or model classed) to both fields and readonly_fields.

Example:

class StatsInline(admin.TabularInline):
    model = Stats
    fields = ('clicked', 'shown', 'avg')
    readonly_fields = ('avg',)
    verbose_name = 'Stats'
    verbose_name_plural = 'Stats'
    can_delete = False

    def avg(self, obj):
        return float(obj.clicked) / obj.shown if obj.shown else 0

P.S. float conversion is needed to avoid casting result to int (e.g. 1/2=0, float(1)/2=0.5)

Reduce directory nesting

Once I encountered a problem with image files that were named according to their checksum of the content chunked by 2 symbols 6 times, so it gets like 2f/d4/e1/c6/7a/2d/28fced849ee1bb76e7391b93eb12.jpg.

To have this structure with approx. 13M files, I got short in inodes. After a quick research and calculations I realized that such nesting depth is redundant and easily can be reduced. So I need to turn all the existing files of form 2f/d4/e1/c6/7a/2d/28fced849ee1bb76e7391b93eb12.jpg to 2f/d4/e1c67a2d28fced849ee1bb76e7391b93eb12.jpg.

To do that, I wrote a script that renames the files and removes empty directories.

TARGET_DIR = '/full/path/to/dir/containing/dirs/to/reduce/'
TARGET_DIR_LEN = len(TARGET_DIR) + 1
CURRENT_DEPTH = 6
DESIRED_DEPTH = 2

last_dir = ''
for dirname, _, filenames in os.walk(TARGET_DIR):
    path = dirname[TARGET_DIR_LEN:].split('/')
    if filenames and len(path) >= CURRENT_DEPTH:
        cur_dir = '/'.join(path[:DESIRED_DEPTH - CURRENT_DEPTH])
        if last_dir != cur_dir:
            last_dir = cur_dir
        for filename in filenames:
            fullpath = os.path.join('/'.join(path), filename)
            parts = fullpath.split('/')
            prefix = ''
            if len(parts[0]) > 2: # cache
                prefix = parts[0]
                parts = parts[1:]
            old = os.path.join(dirname, filename)
            new = os.path.join(TARGET_DIR, prefix,
                               '/'.join(parts[:DESIRED_DEPTH]),
                               ''.join(parts[DESIRED_DEPTH:]))
            pass
            os.rename(old, new)
        for i in range(CURRENT_DEPTH - DESIRED_DEPTH):
            d = os.path.join(TARGET_DIR,
                             dirname[0:(DESIRED_DEPTH - CURRENT_DEPTH + 1) * i]
                             if i else dirname)
            try:
                os.rmdir(d)
            except OSError:
                break

Sync your development environment with a remote one

While the developing process you need sometimes to sync you local development database with a remote one (i.e. production).

Below there is a script allowing to recreate the development database and fill in with data from the remote server.

MySQL

#!/bin/sh

DBUSER_REMOTE="root"
DBPASSWORD_REMOTE="root"
DBUSER_LOCAL="root"
DBPASSWORD_LOCAL="root"
DBNAME_REMOTE=""
DBNAME_LOCAL=""
TMPFILE="$(mktemp db.XXXXXXX)"
HOST="www.example.com"

ssh $HOST "mysqldump -u$DBUSER_REMOTE -p$DBPASSWORD_REMOTE $DBNAME_REMOTE | gzip" | gunzip > $TMPFILE

mysqladmin -u$DBUSER_LOCAL -p$DBPASSWORD_LOCAL -f drop $DBNAME_LOCAL
mysqladmin -u$DBUSER_LOCAL -p$DBPASSWORD_LOCAL create $DBNAME_LOCAL
mysql -u$DBUSER_LOCAL -p$DBPASSWORD_LOCAL $DBNAME_LOCAL < $TMPFILE
rm $TMPFILE

PostgreSQL

#!/bin/sh

DBUSER_REMOTE="postgres"
DBUSER_LOCAL="postgres"
DBNAME_REMOTE=""
DBNAME_LOCAL=""
TMPFILE="$(mktemp db.XXXXXXX)"
HOST="www.example.com"

ssh $HOST "pg_dump -U $DBUSER_REMOTE -Fc $DBNAME_REMOTE" > $TMPFILE

dropdb -U $DBUSER_LOCAL $DBNAME_LOCAL
createdb -U $DBUSER_LOCAL $DBNAME_LOCAL
pg_restore -U $DBUSER_LOCAL -Fc -d $DBNAME_LOCAL $TMPFILE
rm $TMPFILE

Sync media files

$HOST="www.example.com"
$PATH="/absolute/path/to/media"
$LOCAL_DIR="."
rsync -rltDvH $HOST:$PATH $LOCAL_DIR

Favicon sizes

The browser can use the favicon in different situations, like to show it on the tab, for the bookmark and so forth. There are a few sizes the favicon can be. Here I gathered the most often and broadly used.

Favicon sizes

<link rel="icon" type="image/png" sizes="16x16" href="favicon@16.png">
<link rel="icon" type="image/png" sizes="32x32" href="favicon@32.png">
<link rel="icon" type="image/png" sizes="48x48" href="favicon@48.png">
<link rel="icon" type="image/png" sizes="64x64" href="favicon@64.png">
<link rel="icon" type="image/png" sizes="128x128" href="favicon@128.png">
<link rel="shortcut icon" href="favicon.ico">

Apple Icons (used sizes)

<link rel="icon" type="image/png" sizes="144x144" href="favicon@144.png">
<link rel="icon" type="image/png" sizes="512x512" href="favicon@512.png">
<link rel="apple-touch-icon" type="image/png" sizes="57x57" href="favicon@57.png">
<link rel="apple-touch-icon" type="image/png" sizes="144x144" href="favicon@144.png">

PyCharm can't run a project with MySQL database

I wanted to run my project in PyCharm IDE and got this error.

django.core.exceptions.ImproperlyConfigured: Error loading MySQLdb module: dlopen(/Users/boris/env/lib/python2.7/site-packages/_mysql.so, 2): Library not loaded: libmysqlclient.18.dylib
  Referenced from: /Users/boris/env/lib/python2.7/site-packages/_mysql.so
  Reason: image not found

After googling a while I figured out there is a mess with DYLD_LIBRARY_PATH environment variable. So, first I needed to locate the path where libmysqlclient.18.dylib located.

$ locate libmysqlclient.18.dylib
/usr/local/mysql-5.5.22-osx10.6-x86_64/lib/libmysqlclient.18.dylib

Done. In Run/Debug Configurations in Environment variables I added (plus to PYTHONUNBUFFERED=1) DYLD_LIBRARY_PATH=/usr/local/mysql-5.5.22-osx10.6-x86_64/lib/:$DYLD_LIBRARY_PATH.

It started working.

Fatal Python error: Couldn't create autoTLSkey mapping

My last project I started with Django 1.4 and Django Compressor. Today I decided to deploy to the production its first version. I used nginx+Apache.

Everything seemed to be good but instead of normal page I got:

FilterError at /
Unable to apply CompilerFilter (lessc {infile} {outfile})

I tried to repeat the same with ./manage.py runserver. It works. So the issue not in configuration or lessc itself. Later I found here that it is Apache's issue and can be solved with

WSGIApplicationGroup %{GLOBAL}

directive in Apache's VirtualHost config.

It helped.

Install MySQL on Mac OS X to work with Python

I need to get mysql support for python on my Mac OS X Lion.

Download the latest MySQL .DMG distributive from somewhere (i.e. official website) and install it.

sudo pip install python-mysql

It requires superuser privileges to get installed.

What may happen:

while installing mysql-python

Downloading/unpacking mysql-python
  Downloading MySQL-python-1.2.3.tar.gz (70Kb): 70Kb downloaded
  Running setup.py egg_info for package mysql-python
    sh: mysql_config: command not found
    Traceback (most recent call last):
      File "<string>", line 14, in <module>
      File "/Users/boris/projects/a1/th4x/build/mysql-python/setup.py", line 15, in <module>
        metadata, options = get_config()
      File "setup_posix.py", line 43, in get_config
        libs = mysql_config("libs_r")
      File "setup_posix.py", line 24, in mysql_config
        raise EnvironmentError("%s not found" % (mysql_config.path,))
    EnvironmentError: mysql_config not found
    Complete output from command python setup.py egg_info:
    sh: mysql_config: command not found

Traceback (most recent call last):

  File "<string>", line 14, in <module>

  File "/Users/boris/projects/a1/th4x/build/mysql-python/setup.py", line 15, in <module>

    metadata, options = get_config()

  File "setup_posix.py", line 43, in get_config

    libs = mysql_config("libs_r")

  File "setup_posix.py", line 24, in mysql_config

    raise EnvironmentError("%s not found" % (mysql_config.path,))

EnvironmentError: mysql_config not found

----------------------------------------
Command python setup.py egg_info failed with error code 1
Storing complete log in /Users/boris/.pip/pip.log

solution:

Add /usr/local/mysql/bin/ to PATH

export PATH=/usr/local/mysql/bin/:$PATH

(from my ~/.bashrc)

trying to run dev server

Unhandled exception in thread started by <bound method Command.inner_run of <django.contrib.staticfiles.management.commands.runserver.Command object at 0x10c59bc90>>
Traceback (most recent call last):
  File "/Library/Python/2.7/site-packages/django/core/management/commands/runserver.py", line 88, in inner_run
    self.validate(display_num_errors=True)
  File "/Library/Python/2.7/site-packages/django/core/management/base.py", line 249, in validate
    num_errors = get_validation_errors(s, app)
  File "/Library/Python/2.7/site-packages/django/core/management/validation.py", line 35, in get_validation_errors
    for (app_name, error) in get_app_errors().items():
  File "/Library/Python/2.7/site-packages/django/db/models/loading.py", line 146, in get_app_errors
    self._populate()
  File "/Library/Python/2.7/site-packages/django/db/models/loading.py", line 64, in _populate
    self.load_app(app_name)
  File "/Library/Python/2.7/site-packages/django/db/models/loading.py", line 78, in load_app
    models = import_module('.models', app_name)
  File "/Library/Python/2.7/site-packages/django/utils/importlib.py", line 35, in import_module
    __import__(name)
  File "/Users/boris/projects/a1/th4x/tradecontrol/models.py", line 4, in <module>
    from tradecontrol.db import auto_detect
  File "/Users/boris/projects/a1/th4x/tradecontrol/db/__init__.py", line 2, in <module>
    import MySQLdb as mysql
  File "/Library/Python/2.7/site-packages/MySQLdb/__init__.py", line 19, in <module>
    import _mysql
ImportError: dlopen(/Library/Python/2.7/site-packages/_mysql.so, 2): Library not loaded: libmysqlclient.18.dylib
  Referenced from: /Library/Python/2.7/site-packages/_mysql.so
  Reason: image not found

solution:

Add to your ~/.bashrc add

export DYLD_LIBRARY_PATH=/usr/local/mysql/lib

and then reread .bashrc

. ~/.bashrc

Dealing with Tabs in vim

To insert space characters whenever the tab key is pressed, set the 'expandtab' option:

:set expandtab

With this option set, if you want to enter a real tab character use Ctrl-V<tab> key sequence.

To control the number of space characters that will be inserted when the tab key is pressed, set the 'tabstop' option. For example, to insert 4 spaces for a tab, use:

:set tabstop=4

After the 'expandtab' option is set, all the new tab characters entered will be changed to spaces. This will not affect the existing tab characters. To change all the existing tab characters to match the current tab settings, use:

:retab

To change the number of space characters inserted for indentation, use the 'shiftwidth' option:

:set shiftwidth=4

For example, to get the following coding style,
*No tabs in the source file.
*All tab characters are 4 space characters.

use the following set of options:

:set tabstop=4
:set shiftwidth=4
:set expandtab

Add the above settings to your .vimrc.