Showing entries with tag "Python".

Found 3 entries

Python: Null coallesce on an array

I have a small array in Python, and I need to get the 2nd element of that array, or a default value if it's not present. All the other languages (PHP, Perl, Javascript) I use have a simple null coallescing operator that makes it simple, but not Python. I got tired of writing it out every time to so I wrote a simple wrapper function:

x = [2,4,6]

# Get the 3rd item from x
y = arrayItem(2, x, -1) # 6
# Get the 8th (non-existent) item from x
y = arrayItem(7, x, -1) # -1
# Get an item from an array, or a default value if the array isn't big enough
def arrayItem(needle, haystack, default = None):
    if needle > (len(haystack) - 1):
        return default
        return haystack[needle]

If there is a better, simpler, built-in way I'm open to hearing it.

Leave A Reply - 1 Reply

Perl: A script that contains valid Perl and Python code

Perl has a cool runtime option named -x that causes Perl to scan a file for the first shebang line with perl in it, and start executing there. This allows you to embed Perl in other files, like text files, or email files.

This got me thinking about embedding a working Perl script in another file. Python allows you to have large multi-line comment blocks using triple quotes """ blocks around your text. Using these comment blocks I was able to embed Perl code inside of a Python script. Effectively you can have a single file that is executable by Perl (with -x) and Python. I wrote up a quick proof-of-concept dual language script.

perl -x

Gives varying output:

Hello world from Python v3.8.7
Hello world from Perl v5.30.3
Leave A Reply

PHP: Quote Word

I needed a function similar to Perl's qw. If you pass a string to this function it will return an array of the words, stripping any separating whitespace. If you pass true as the second parameter you will instead get a hash returning each word in a key/value pair.

function qw($str,$return_hash = false) {
    $str = trim($str);

    // Word characters are any printable char
    $words = str_word_count($str,1,"!\"#$%&'()*+,./0123456789-:;<=>?@[\]^_`{|}~");

    if ($return_hash) {
        $ret = array();
        $num = sizeof($words);

        // Odd number of elements, can't build a hash
        if ($num % 2 == 1) {
            return array();
        } else {
            // Loop over each word and build a key/value hash
            for ($i = 0; $i < $num; $i += 2) {
                $key   = $words[$i];
                $value = $words[$i + 1];

                $ret[$key] = $value;

            return $ret;
    } else {
        return $words;

This is useful in the following scenarios:

$str  = "Leonardo    Donatello    Michelangelo    Raphael";
$tmnt = qw($str);

$str = "
    Leonardo       Blue
    Donatello      Purple
    Michelangelo   Orange
    Raphael        Red
$turtles = qw($str,true);

Here is a similar function written in Python 3.x:

xarray = qw("reg blue green orange yellow")
def qw(xstr):
    ret = xstr.strip().split()

    return ret
Leave A Reply