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TypeError: list indices must be integers

March 8, 2010 by Jason Garber

You start your day, happily working with dictionaries…Life is good.

>>> mydict = {'key-a': 'value-a', 'key-b': 'value-b'}
>>> mydict['key-a']
'value-a'

All of a sudden, storm clouds appear. Your dictionary variable accidentally gets assigned a list, and life is no longer good!

>>> mydict = {'key-a': 'value-a', 'key-b': 'value-b'}
>>> mydict['key-a']
'value-a'
>>> mydict = []
>>> mydict['key-a']
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: list indices must be integers

The error message "TypeError: list indices must be integers" is generated when you attempt to use a non-int for a index inside the [] operator.

By the way, almost the same message is used if you do this with a tuple:

TypeError: tuple indices must be integers

Posted in Engineering, Technique | Tagged , , , , | Leave a Comment »

nginx restart error

February 24, 2010 by Jason Garber

Was playing around with nginx on Centos 5 (EPEL package).

Most of the time I ran:

service nginx restart

I would get this message in the /var/log/nginx/error.log file:

panic: MUTEX_LOCK (22) [op.c:352].

After some hunting around, it appears to be a known bug in nginx (perhaps perl in nginx?)… Anyway, a simple workaround is to do this:

service nginx stop
service nginx start

Or, simply edit /etc/init.d/nginx, and add the sleep 1 line:

51 restart() {
52     configtest || return $?
53     stop
54     sleep 1
55     start
56 }

Nice workround!

Posted in Linux, System Administration, Technique | Tagged , , | Leave a Comment »

Great article on Python super, __mro__, and attributes

February 20, 2010 by Jason Garber

I highly recommend reading this excellent writeup on Python super(), python __mro__, python attributes, and more.

It is Copyright © 2005-2009 Shalabh Chaturvedi

http://www.cafepy.com/article/python_attributes_and_methods/python_attributes_and_methods.html#method-resolution-order

Posted in Engineering, Open Source, Perspective, Technique | Tagged , , , | Leave a Comment »

git scm tip

February 20, 2010 by Jason Garber

You may be aware of git add .

But did you know this:

git add .

adds all the files. Use with care (only after git status, for example).

git add -u .

adds and deletes all KNOWN files.

This is great if you added and removed or renamed files.

Posted in Engineering, Perspective, Technique | Tagged , , , | Leave a Comment »

Is it just me, or does this get old?

January 12, 2010 by Jason Garber

Hi Darryll,

If I have to say no again, you will officially be a nuisance. Have a great day, and best wishes with your endeavors.

–

Best Regards,

Jason Garber
Senior Systems Engineer
AppCove, Inc.

On Tue, Jan 12, 2010 at 10:35 AM, Darryll ——— wrote:

Jason,

I don’t mean to be a nuisance, but I wanted to try one more time to see if you, or someone you could direct me to would have a couple of minutes to discuss how my company can increase your access to working capital, a process which the Wall St. Journal calls, ‘An idea whose time has come.’ Just reply to my email, or contact me at the number below and I’ll follow up with you.

Best,

Darryll ——–
504———–

Posted in Perspective | Tagged | 1 Comment »

Google’s Lack of Customer Support

January 9, 2010 by Jason Garber

Perhaps it’s because Google hasn’t had “traditional customers” en mass for so long? Perhaps it’s because Google is 99% full of techno-geeks that are very focused on technology? Perhaps it’s just a lack of management’s vision?

Regardless of the reason, it’s hard to dispute that Google, Inc. lacks in Customer Service. Most recent post I saw was this Computer World article on the Nexus One fiasco.  Or just search google for the issue.

In my own experience with Google at work, I’ve had horrible, terrible, and just downright non-existent support on critical issues with Google Apps and Google Enterprise Support (both of which we are a paying customer).

A 7 day response time is about as good as a 700 day response time in today’s business world.  A phone number which we pay to have access to that is not answered in a time of need?  Unanswered requests by email and web forms?

Google has figured out how to manage vast quantites of talent to produce a wide array of successful products.  But if they continue to ignore their paying customers, it will take a toll on them that will be beyond repair.

If Google is reading this, remember that bad word of mouth is 100 times as fast spreading as good word of mouth.  I encourage you, Mr. Schmidt, to apply a resonable fraction of your vast resources to create the best customer service experience in the world.   Then, you will truly, do no evil.

Posted in Perspective | Tagged , , | Leave a Comment »

Python 3 bytes indexing returns integers!

December 31, 2009 by Jason Garber

While converting a bunch of werkzeug code to Python 3.1, I ran into an issue with one of the bytes objects that was previously a string.

The line of code in question was originally this:

if value and value[0] == value[-1] == b'"':
   ...

If value is something, and the first and last characters are a quote character, then…

However, as it turns out, the bytes object is actually a list of integers in the range of 0-255.

So when you use an indexing operation on a byte, you actually get an integer back. For example:

>>> x = b'Hello World'
>>> x[0]
72

>>> x = 'Hello World'
>>> x[0]
'H'

Big difference, eh?

Posted in Engineering, Technique | Tagged , , | Leave a Comment »

Example Automated MySQL Backup Script

December 26, 2009 by Jason Garber

Rather than use --all-databases, which will prevent you from being able to selectively restore any single database, consider the following:

Ideally, you should have a daily backup, with some history. It should be bulletproof (--force), it should be logged (>> ...log), it should be compressed (| gzip), it should keep separate copies of each database, and it should automatically pick up any databases that are added.

Consider, rather, a shell script like this:

#!/bin/bash

Host=server.domain.com
BDir=/home/backup/backup/mysql

Dump="/usr/bin/mysqldump --skip-extended-insert --force"
MySQL=/usr/bin/mysql

Today=$(date "+%a")

# Get a list of all databases
Databases=$(echo "SHOW DATABASES" | $MySQL -h $Host)

for db in $Databases; do
        date=`date`
        file="$BDir/$Host-$db-$Today.sql.gz"
        echo "Backing up '$db' from '$Host' on '$date' to: "
        echo "   $file"
        $Dump -h $Host $db | gzip > $file
done

Which is assuming that you have a file ~/.my.cnf (chmod 600), that has:

[client]
user = "BACKUP"
password = "SOMEPASS8342783492"

Make sure that whatever user you are using for BACKUP has this grant statement:

GRANT
  SELECT, SHOW VIEW ON *.*
  TO BACKUP@localhost
  IDENTIFIED BY 'SOMEPASS8342783492';

So simply add this to a nightly cronjob, and you have a daily backup that rotates each 7 days week.

0 3 * * *   backup-mysql >> backup-mysql.log 2>> backup-mysql.log

The backup directory then contains:

-rw-r--r-- 1 backup backup 2217482184 Sep  3 13:35 base.appcove.net-VOS4_0-20090903.sql.gz
-rw-rw-r-- 1 backup backup 2505876287 Dec 25 00:48 base.appcove.net-VOS4_0-Fri.sql.gz
-rw-r--r-- 1 backup backup 2500384029 Dec 21 00:48 base.appcove.net-VOS4_0-Mon.sql.gz
-rw-r--r-- 1 backup backup 2506849331 Dec 26 00:48 base.appcove.net-VOS4_0-Sat.sql.gz
-rw-r--r-- 1 backup backup 2499859469 Dec 20 00:48 base.appcove.net-VOS4_0-Sun.sql.gz
-rw-rw-r-- 1 backup backup 2505046147 Dec 24 00:48 base.appcove.net-VOS4_0-Thu.sql.gz
-rw-rw-r-- 1 backup backup 2502277743 Dec 22 00:48 base.appcove.net-VOS4_0-Tue.sql.gz
-rw-r--r-- 1 backup backup 2504169910 Dec 23 00:48 base.appcove.net-VOS4_0-Wed.sql.gz
-rw-r--r-- 1 backup backup   76983829 Dec 25 00:49 base.appcove.net-VOS4_Mail_0-Fri.sql.gz
-rw-r--r-- 1 backup backup   76983829 Dec 21 00:49 base.appcove.net-VOS4_Mail_0-Mon.sql.gz
-rw-r--r-- 1 backup backup   76983829 Dec 26 00:49 base.appcove.net-VOS4_Mail_0-Sat.sql.gz
-rw-r--r-- 1 backup backup   76983829 Dec 20 00:48 base.appcove.net-VOS4_Mail_0-Sun.sql.gz
-rw-rw-r-- 1 backup backup   76983829 Dec 24 00:49 base.appcove.net-VOS4_Mail_0-Thu.sql.gz
-rw-rw-r-- 1 backup backup   76983829 Dec 22 00:49 base.appcove.net-VOS4_Mail_0-Tue.sql.gz
-rw-r--r-- 1 backup backup   76983829 Dec 23 00:49 base.appcove.net-VOS4_Mail_0-Wed.sql.gz
-rw-r--r-- 1 backup backup  304803726 Dec 25 00:49 base.appcove.net-WeSell_0-Fri.sql.gz
-rw-r--r-- 1 backup backup  303480087 Dec 21 00:49 base.appcove.net-WeSell_0-Mon.sql.gz
-rw-r--r-- 1 backup backup  304710121 Dec 26 00:49 base.appcove.net-WeSell_0-Sat.sql.gz
-rw-r--r-- 1 backup backup  303791294 Dec 20 00:49 base.appcove.net-WeSell_0-Sun.sql.gz
-rw-rw-r-- 1 backup backup  305315415 Dec 24 00:49 base.appcove.net-WeSell_0-Thu.sql.gz
-rw-rw-r-- 1 backup backup  302516217 Dec 22 00:49 base.appcove.net-WeSell_0-Tue.sql.gz
-rw-r--r-- 1 backup backup  303314217 Dec 23 00:49 base.appcove.net-WeSell_0-Wed.sql.gz
-rw-r--r-- 1 backup backup     135301 Dec 25 00:30 dc40.appcove.net-mysql-Fri.sql.gz
-rw-r--r-- 1 backup backup     135301 Dec 21 00:30 dc40.appcove.net-mysql-Mon.sql.gz
-rw-r--r-- 1 backup backup     135301 Dec 26 00:30 dc40.appcove.net-mysql-Sat.sql.gz
-rw-r--r-- 1 backup backup     135301 Dec 20 00:30 dc40.appcove.net-mysql-Sun.sql.gz
-rw-rw-r-- 1 backup backup     135301 Dec 24 00:30 dc40.appcove.net-mysql-Thu.sql.gz
-rw-rw-r-- 1 backup backup     135301 Dec 22 00:30 dc40.appcove.net-mysql-Tue.sql.gz
-rw-r--r-- 1 backup backup     135301 Dec 23 00:30 dc40.appcove.net-mysql-Wed.sql.gz

Posted in Linux, System Administration, Technique | Tagged , , , | Leave a Comment »

How to Author a *simple* jQuery plugin

December 21, 2009 by Jason Garber

I use jQuery as the JavaScript library for most projects. It’s terribly convenient for selecting elements and processing them.

However, jQuery is not JavaScript, and there is a lot of things it cannot do. Rather than writing a separate set of functionality outside of jQuery, why not simply extend it on an application-per-application basis? It really is that easy. Perhaps if you get some functionality that is good enough, you will want to convert them into a formal plugin and post it to http://plugins.jquery.com/…

Here is the document that explains, in depth, how to author plugins.
http://docs.jquery.com/Plugins/Authoring

Here is an example at a very simple plugin that I whipped together while learning about plugins… It’s designed to accept an object of data, and apply it to any of the elements whose name attribute match the key of the data.

jQuery.fn.populate = function(Data) {
   this.each(function() {
      if (this.name in Data)
      {
         switch(this.type)
         {
            case 'text': this.value = Data[this.name]; break;
            case 'checkbox': this.checked = Data[this.name]; break
         }
      }
   });
   return this;
};

To call it… Select all input elements of the #Login form, and populate them with the passed data.

$('#Login :input').populate({ FirstName: 'sammy', LastName: 'jones' });

The .fn attribute of the jQuery object is where you attach new methods. The this member of those functions is set to the current jQuery object. The function must return the current jQuery object (self) unless explicitly stated otherwise.

Iterating through the elements of the current jQuery object should be done with this.each(…).

All in all, it’s very simple, and very powerful to be able to nest custom functionality into the jQuery object within a given application.

Read more at:

Posted in Engineering, Technique, Uncategorized | Tagged , , | Leave a Comment »

jQuery mouseout vs. mouseleave

December 18, 2009 by Jason Garber

Hello!

jQuery has a mouseout and a mouseleave event. The main difference is in how they handle child elements. Mouseout fires when the pointer moves into or out from child element, while mouseleave doesn’t.

This was causing a slight problem of having some menu’s close when the mouse encountered a link or other child element within the menu, it was triggering the mouseout event of the menu.

The fix, was to convert to mouseleave.

   $("#Nav1_Content > p").mouseleave(CloseTopMenuArea);

http://docs.jquery.com/Events/mouseout

Posted in Engineering, Technique | Tagged , , | Leave a Comment »

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