Lior Gradstein's Blog

Django: How to find the url/path you’re into, in a template loaded by a generic view

Lior Gradstein — Thu, 19 Mar 2009 22:11:39 +0000

In a Django project, I have a template that is used by two urls, which is quite common (generic views, using ‘create_object’ and ‘update_object’). The problem is that I had to add a supplementary menu just when the template is loaded from the ‘update’ generic view, and not from the ‘create’ generic view.

Making the difference between the two urls calls at the template level is a problem because it’s managed by generic views, so the same template is used.

Anyways, there are several possibilities:

In urls.py, use the ‘template_name’ variable, where you can speficy a specific template for this url(). That is instead of using the default _form.html.
What I don’t like in this situation, is that I will have two nearly similar templates, just for an added menu. Not cool. Another problem is that I use a loop to create all my urls. So if I add a special template, I’ll add it to ALL my models :-(.

Another solution, is to find a way to use a variable in the template that would be different wether the template has been loaded by update_object or create_object.

In our urlpatterns in urls.py, we can use the ‘extra_context‘ variable (takes a dictionnary as parameter). It is correctly managed, even when using generic views. So, you’ll have :

url(r‘foo/ajouter/$’, ‘django.views.generic.create_update.create_object’,  
dict(form_class=modelForm,

                extra_context={‘usage’:‘create’},

                name=‘foo_create’,))
url(r‘foo/%s/(?P\d+)/modifier/$’,

                ‘django.views.generic.create_update.update_object’,

                dict(form_class=modelForm,

                extra_context={‘usage’:‘modify’},

                name=‘foo_update’))

We can also use, in urls.py, the ‘context_processors’ variable. For more information about the context processors, have a look at this tutorial. The goal is to add ‘django.core.context_processors.request’, like this:

from django.core.context_processors import request

and in the url(), add context_processors:

url(r‘foo/ajouter/$’, ‘django.views.generic.create_update.create_object’,  

                dict(form_class=modelForm,

                context_processors=[request,]),

                name=‘foo_create’,))

The last possiblity is a more global solution. It’s like the context_processors usage above, but added into every templates automatically.
To do this, you’ll have to edit the list of Template Processors in your settings.py file. That list is run each time a template is loaded, and allows one to add any variable to the template automatically. By default (on Django 1.0.x) this list is commented out, so it has by default the list:

("django.core.context_processors.auth",

"django.core.context_processors.debug",

"django.core.context_processors.i18n",

"django.core.context_processors.media")

You’ll have to uncomment it, and add ‘django.core.context_processors.request’. By doing this, you get the variable ‘request.path’ available in your template.

Finally, you’ll be able to test your variable with {% ifequal %} and display your conditional elements.

calcubetimer moved to Google Code

Lior Gradstein — Thu, 19 Mar 2009 16:51:08 +0000

Calcubetimer’s website doesn’t seem to work anymore :-( Fortunately, gnehzr has moved the code to Google Code.

Asterisk cirpack problem with Free and freephonie.net

Lior Gradstein — Thu, 12 Feb 2009 09:34:51 +0000

If you configured your Asterisk/FreeSWITCH server to talk to your freephonie.net (french Free ISP provider), you’ll see in the logs the following warning message:

[Feb 12 09:29:06] WARNING[9228]: chan_sip.c:6624 determine_firstline_parts: Bad request protocol Packet

This is not really a problem, but an annoyance, as it fills up your logs. This is a known problem for more than years, but has never been corrected (neither by Asterisk nor by Cirpack devs). The usual correction was to add the following line to your startup scripts (/etc/rc.local on Debian for example):

iptables -A INPUT -p udp -m udp –dport 5060 -m string –string "Cirpack KeepAlive Packet" -j DROP

But the syntax has changed in iptables, and you’ll get the error:

iptables v1.3.6: STRING match: You must specify `–algo‘

so, just add one of the 2 available algorithms (bm and kmp):

iptables -A INPUT -p udp -m udp –dport 5060 -m string –string "Cirpack KeepAlive Packet" –algo bm -j DROP

Easy chess games for kids (mate in one)

Lior Gradstein — Mon, 02 Feb 2009 00:45:12 +0000

In my journey to teach chess to Ido, an easy (I thought) job was to generate diagrams where he has to find mate in a fixed number of turns. Starting with mate in one.
It appeared that making diagrams is an easy task, as there are many programs (Linux and Windows) that permit this.
On Linux, the best I could find is scid. That’s cool as I use it to maintain my databases of games. Even cooler, is that scid development has just restarted (stopped around 2004!), with the help of Pascal Georges. Using scid (I’m using the 3.7devel2009 version) I can export games to HTML or even to LaTeX files.

At first I thought I’d create the endings myself, for example, using online diagrams generators or using Wikipedia/MediaWiki’s templates, but it was not so easy, so I thought about making a program to generate them.
Generating one from scratch would take me time I really don’t have, and there are just two python modules that give high-level functions to chess.
So I started looking for projects similar to mine, that include games with mate in one. I found a small database of mate in one on my favorite chess website, in the download section: a Chessbase datafile with 1171 mate in one studies! So cool.

Well, It was really a pain to convert that Chessbase (.cbv) file, as the only program able to convert to PGN is running on Windowsã€€(at least it’s free). You just have to follow the instructions from this thread.
After getting a nice PGN file, just open it with scid, go to “Tools”, then select “Write the filter”, and choose LaTeX. You’ll get a TeX file. Use you favorite TeX generator (Live TeX seems to be the one today), like this for example, to generate directly a PDF file:

cat mat_temp.tex |grep -v "\\\\$" > mate_in_one.tex

latex –output-format=pdf mate_in_one.tex

(Yes I had to cleanup a bit the file before generating the .pdf)

The result is here, 196 pages of tests (6 one each page) if you don’t want to fight with the missing TeX modules (you’ll need chess12.sty) and get a nice result.

I’m sure many people search for this kind of file, so I’m pretty happy to help other parents/coaches.

White mate in one

Edit: I added a PDF version without the solution included.

Ido’s chess Journey: How to teach chess to a 3 year old kid

Lior Gradstein — Wed, 28 Jan 2009 01:20:24 +0000

How to teach chess to a 3 year old kid? That’s a good question. I wanted to teach Ido chess for a long time, but each time I tried, he lost focus after 2 minutes, even just for teaching him just rook movements.
I decided I needed to plan it a little more, make it much more fun, and “embed” it in mini-games. It seems to work much better now, but that’s maybe because he matured a lot.

Here are some ideas (some not yet implemented):

Using a DIY plastified chess board, allows me to show/play different positions really fast, anywhere.
Colorize squares where a piece is allowed to go :

view on flickr»" rel="lightbox">
Pawn race games (no en-passant rule yet).
Really small games (must not go over 5 minutes) with reduced chess set (for example Queen and 3 pawns vs Knight, bishop and 3 pawns).
Checkmate in one, using DiagTransfer program to draw series of chess diagrams. This program works only on Windows, but it works fine with Wine.

view on flickr»" rel="lightbox">

For quick single diagrams, I found wbeditor, an online javascript diagram generator.

There’s a thread (french) about experience from different teachers, giving really good advices.
Most notably, VÃ©ronique Houck who has 15 years of experience of teaching chess to kindergarten/maternelle children. She wrote two books (in french). One is named Bibou & le monde des Ã©checs, and the other one Le jeu d’Ã©checs au cycle2. It’s not so easy to find, but using Google, you can find shows many links.

I’ve not yet read them. I’ll make a review when I get them.

Python snippet to get Mediawiki/Wikipedia Recent Changes externally

Lior Gradstein — Tue, 27 Jan 2009 23:37:35 +0000

Mediawiki allows one to send Recent Changes (RC) to a UDP port.
The ip address is defined by the variable wgRC2UDPAddress, and the port by the variable wgRC2UDPPort. It’s a really good idea that it’s a UDP transfer, since there is no need for any ACK, so Mediawiki doesn’t block if there is nothing listening on that port.

These parameters must be set in the LocalSettings.php file, like this, for example.

$wgRC2UDPAddress = ‘127.0.0.1′;

$wgRC2UDPPort = 9390;

I wrote a really simple python program (more a proof of concept) that receives the data, cleans it, and then prints it to stdout :

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# vim:syntax=python:sw=4:ts=4:expandtab
importSocketServer
importre
HOST,PORT = ”, 9390
class MyUDPHandler(SocketServer.BaseRequestHandler):

   def handle(self):

       print re.sub(r‘\x03\d{0,2}’, ”, self.request[0])
if __name__ == ‘__main__’:

   server = SocketServer.UDPServer((HOST, PORT), MyUDPHandler)

   server.serve_forever()

I plan to make it into a complete project that will send the data/notifications using Jabber(XMPP).

How to skip the useless “you are now logged in” page in Mediawiki

Lior Gradstein — Sat, 17 Jan 2009 23:47:38 +0000

You installed Mediawiki some time ago, and now something bothers you: aren’t you tired of having an intermediate page named “Login successful” saying “You are now logged in to” before being allowed to go to the page you wanted to go? I am.
I found there’s a hook that is called just when a user successfully logs on (UserLoginComplete), and even an extension named RedirectOnLogin that does the redirection for you, BUT to a fixed one. It seems the hook doesn’t give you the page you previously were before the login request.

So to correct this, I just found a dirty hack. That means you’ll have to patch the source, meaning also that you’ll loose some flexibility when upgrading Mediawiki :-(
Anyway, if you still want to do this, here is the magic stuff:

Edit the file mediawiki/includes/specials/SpecialUserlogin.php and look for the function successfulLogin().
At the end of it, just add (it’s just one line):

header(‘Location: ./index.php?title=’ . $this->mReturnTo);

That’s it. You’ll get redirected to the previously accessed page automatically! Really cool.

This has been successfully used on a Mediawiki 1.13.

How to dial a number using Asterisk and Python

Lior Gradstein — Wed, 17 Dec 2008 09:39:17 +0000

I didn’t find any example in Python on how to Dial a number from an Asterisk server and link it to another channel. So here’s a quick code to do it. You just need to have a manager defined in your /etc/asterisk/manager.conf defined.

importsocket
HOST="192.168.1.116"

PORT=5038
p = """Action: login

Events: off

Username: %(username)s

Secret: %(password)s
Action: originate

Channel: SIP/%(local_user)s

WaitTime: 60

CallerId: 600

Exten: %(phone_to_dial)s

Context: default

Priority: 1
Action: Logoff

"""

def click_to_call(phone_to_dial, username, password, local_user):

    pattern = p % {

            ‘phone_to_dial’: phone_to_dial,

            ‘username’: username,

            ‘password’: password,

            ‘local_user’: local_user}
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

    s.connect((HOST, PORT))
    data = s.recv(1024)

    for l in pattern.split(‘n’):

        print "Sending>", l

        s.send(l+‘rn’)

        if l == "":

            data = s.recv(1024)

            print data

    data = s.recv(1024)

    s.close()
if __name__ == ‘__main__’:

    click_to_call(phone_to_dial=‘123456789′,

                  username=‘manager_login’, password=‘yourpass’,

                  local_user=‘600′)

Synchronization methods of a file with Puppet

Lior Gradstein — Mon, 29 Sep 2008 12:39:32 +0000

Usually, to synchronize a file with remote hosts, using puppet, one would use the following pattern:

file { "/etc/init.d/pvfs2-server":

      owner => root, group => root, 

      mode => 755, 

      source => "puppet:///files/pvfs2-server"    

}

(using “source” to copy data as-is, and using “template(”filename”) to use a template structure as data).

Or, if one wishes to directly set the content of the target file:

file { "/etc/init.d/pvfs2-server":

   owner => root, group => root, 

   mode => 755, 

   source => "puppet:///files/pvfs2-server"    

}

Please note that on the first line, for example ‘file { “/etc/mpd.conf”:’), the “/etc/mpd.conf” is a merge of two functionalities/concepts: Usually, the syntax is clear and simple:

file { mon_fichier_mpd_conf:

     path => "/etc/mpd.conf",

     […]

}

The first line is about the resource description. Its goal is to be able to reference to it a little later from another resources (Notify[], etc.). By putting directly the file path and name (I think it’s identified as a filename and not as a description because there are quotes, or maybe it’s because it begins with a slash?) you mege the “path” attribute with its description.
On the other end, we’ll not be able to reference to it later, if you need to.

You may also need to synchronize a file that is not present in the repository (puppet:///files/*). That usually happens, for example, when that file is regenerated by an external program or an external action (like /etc/passwd).

file {"/etc/passwd":

     owner => root, group => root, mode => 644,

     content => file("/etc/passwd")

}

How to automatically run a script after inserting a USB device on Ubuntu?

Lior Gradstein — Sun, 13 Apr 2008 21:32:01 +0000

Here’s the setup: you have a computer which has a SD port (small memory cards, mostly used in cameras, phones, etc.). You want to get all of your photos from that card automatically as soon as you insert your card (may be a USB key as well), that is, run a script which will search for all of your photos, and copy them to a local directory.

I know, some programs already do this, but they require Xwindow and some ugly Gnome/KDE app. What we’re doing here is a minimal setup, using the least memory.

Normally, on a normal Unix system you would use the included device detection mechanism, which is hotplug. But on Ubuntu (at least Gutsy and Hardy), the de-facto/required way is by using udev, which is an event based system, using rules to fire new events/mount/symlink or run programs according to some patterns defined as “rules”.

So, the first thing to do is to identify your device according to USB events. udevinfo is your friend. So, after looking at the output of dmesg, you’ll see your USB device is available on some sd* device.

So run:

 udevinfo -a -p  /sys/block/sda

(replace sda with you device)

You will get a list of “blocks” representing each layer of drivers. For example:

root@sleek:/etc/udev/rules.d# udevinfo -a -p /sys/block/sda/
looking at device ‘/block/sda’:

KERNEL=="sda"

SUBSYSTEM=="block"

DRIVER==""

ATTR{stat}=="  229567    [...] 456048  3697068"

ATTR{size}=="488397168"

ATTR{removable}=="0"

ATTR{range}=="16"

ATTR{dev}=="8:0"
looking at parent device ‘/devices/pci0000:00/00[...]:

KERNELS=="2:0:0:0"

SUBSYSTEMS=="scsi"

DRIVERS=="sd"

ATTRS{ioerr_cnt}=="0×0"

ATTRS{iodone_cnt}=="0xcc26b"

ATTRS{iorequest_cnt}=="0xcc26c"

ATTRS{iocounterbits}=="32"

ATTRS{timeout}=="30"

ATTRS{state}=="running"

ATTRS{rev}=="3.AA"

ATTRS{model}=="ST3250310AS     "

ATTRS{vendor}=="ATA     "

These are in fact attributes that you can use in your rule to filter the devices. So for example,
to run a shell script when a SCSI device is detected which has a size of 1GB, I’ll use the following line:

KERNEL=="sd?1", ATTRS{size}=="1999872", RUN+="/usr/local/bin/recup_usb.sh"

This line is to be put in a new file in /etc/udev/rules.d, named something like 91-backuptousbdrivetrigger.rules. It’s better to put the file at the end of the rules (the “91″), as not to disturb other module loadings.

The content of the recup_usb.sh file can be:

#!/bin/bash
if [ "${ACTION}" = "add" ]; then

   rm -rf /tmp/x

   mkdir /tmp/x

   mount -t vfat /dev/sdc1 /tmp/x

   find /tmp/x -name "*jpg" -exec /usr/bin/rsync -avz {}  \

              /home/foobar/Pictures/Incoming/`date +%Y-%m-%d`/ \;

   umount /tmp/x

fi

(yes, I know this code is dirty, I should have used mktemp, but you get the point…)
Don’t forget to chmod +x the shell script and reload the configuration with:

udevcontrol reload_rules

For more detailed information about writing udev rules, take a look at the official documentation, or another’s detailed information about doing the same thing.

Lior Gradstein's Blog

Django: How to find the url/path you’re into, in a template loaded by a generic view

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calcubetimer moved to Google Code

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Asterisk cirpack problem with Free and freephonie.net

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Easy chess games for kids (mate in one)

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Ido’s chess Journey: How to teach chess to a 3 year old kid

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Python snippet to get Mediawiki/Wikipedia Recent Changes externally

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How to skip the useless “you are now logged in” page in Mediawiki

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How to dial a number using Asterisk and Python

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