Count number of elements in array - PHP, Perl, Python

We often need to count the number of elements in an array (or get the size of an array). Here is how to do it in PHP, Perl & Python:

PHP: $items = count($ara);

Perl: my $items = scalar(@ara);, you can also try: my $items = @ara;

Python: items = ara.__len__(). Note that in Python it's called list. List can be used as array.

execute linux command using Perl, Python, PHP

Those who program in Linux often need to execute/run linux commands from programs/scripts.

Using python you can execute linux command is the following way:

import os
os.system('ls -lt')


If you use Perl, you can do it in the following ways:
1. system(mkdir $folder);
2. qw(mkdir $folder);
3. $temp = `mkdir $folder`; #back ticks
4. exec($command);

If you use back ticks or qw, $? will be set if any error occurs. So you can use it like this:

qw(rm $filename);
if($?) {
print STDERR "error deleting file\n";
}


There are also several options available to run linux commands using PHP. Take a look at here for detals: http://us2.php.net/manual/en/ref.exec.php

Use Beautiful Soup for Screen Scraping in Python

What to speed up web crawler / spider development? Try Beautiful Soup, if you use Python.

From their website:

Beautiful Soup is a Python HTML/XML parser designed for quick turnaround projects like screen-scraping. Three features make it powerful:

1. Beautiful Soup won't choke if you give it bad markup. It yields a parse tree that makes approximately as much sense as your original document. This is usually good enough to collect the data you need and run away.
2. Beautiful Soup provides a few simple methods and Pythonic idioms for navigating, searching, and modifying a parse tree: a toolkit for dissecting a document and extracting what you need. You don't have to create a custom parser for each application.
3. Beautiful Soup automatically converts incoming documents to Unicode and outgoing documents to UTF-8. You don't have to think about encodings, unless the document doesn't specify an encoding and Beautiful Soup can't auto detect one. Then you just have to specify the original encoding.

You can download it from here: http://www.crummy.com/software/BeautifulSoup/

Ruby programmers can enjoy Rubyful Soup

Enjoy High Speed Spider development with Beautiful Soup!