php | perl | perlr | python

....
k = key
v = value
i = numeric iterator
b = boolean
s = string
n = number
a = array
rx = regular expression

comment - best practice for language at top

Booleans

php

true, false
Evaluates to false: 0,'',null,false,array() (empty array)
Everything else evaluates to true

case-insensitive. print true; will output '1', print false; will output ''

perl

0, '', undefined variables => all evaulate to false
1, everything else => all evaluate to true

there is no boolean datatype. print true; will output '1', print false; will output ''

python

True, False
Evaluates to false: False, None, '', 0, [], {}, ()
Everything else evaluates to true

names use initial caps

ruby

true,false - lowercase only
Evaluates to false: false, nil
Everything else evaluates to true, including 0, empty arrays and empty objects

Null + other

php

null

case insensitive

perl

null

case insensitive

python

None

case sensitive

Division

php

10/3 = 3.333

behaves as you'd expect

python

10/3 # 3 - int/int is floored int
10/3.0 # 3.3333.. - int/float is standard float
10//3.0 # 3.0 int//float is floored float

ruby

10/3 # 3 - int/int is floored int
10/3.0 # 3.3333.. - int/float is standard float
10/3.to_f # 3.3333..

Numeric power

Mod

php

$n = 4%3; // 1
$n = 4.5%3; // 1
#res = $n == 1.5;

converts arguments to integers

For loop over an array

php

foreach($a as $v)

php5 can use &$v to create a reference

php

foreach($a as $i => $v)

php

for($i=0;$i<count($arr);$i++)

perl

for $v (@array)

including $v means that $_ won't be created

perl

for ($i=0;$i<=$#a;$i++) {
$v = $a[$i];
}

$#a is the last position in the array, i.e. @a = (1,2,3); $#a == 2;

python

for i in a:
v = a[i]

python

for v,i in zip(a,range(len(a))):

ruby

a.each_with_index do |v,i|

ruby

a.each{|v| v }

uses braces instead of do & end

javascript

for (var i=0;i<a.length;i++) {
var v = a[i];
}

cannot use for (var v in a) because this will include .length

For loop over a hash

php

foreach ($arr as $k => $v) {}

with key iterator

php

foreach ($arr as $v) {}

php

array_walk($h,create_function('&$v,$k','
$v += 1;
'));

need to single quote strings else $var will get parsed

perl

for $k (keys %hash) {
$v = $hash[$k];
}

including $k means that $_ won't be created

perl

for $s (%hash) {}

$s will output $k then $v, so is basically useless

python

for k in h:
v = h[k]

ruby

h.each do |k,v|

javascript

for (var k in h) {
var v = h[k];
}

Statement modifiers slash tenary operators

php

$s = $b ? 'o' : 't';

perl

print 'hello' if 1;

python

s = 'o' if b else 't'

ruby

print 'hello' if true
x = x + 1 while x < 100

Scalar construction

javascript

var s = 'abc';

Scalar referencing

perl

$s2 = \$s;

you need to deference $$v2 before you can do anything with it

Scalar cloning

Trim

python

s2 = s.strip()

see http://docs.python.org/library/stdtypes.html#string-methods for more string methods, also http://en.wikibooks.org/wiki/Python_Programming/Strings

perl

sub trim { $_[0] =~ /^\s*?(.*?)\s*$/; return $1; }

perl doesn't have a built in trim function

Upper case string

php

$s2 = strtoupper($s);

python

s2 = s.upper()

Lower case strimg

php

$s2 = strtolower($s);

python

s2 = s.lower()

Upper case first letter of a string

python

s2 = s.capitalize()

perl

$s2 = ucfirst($s);

use lcfirst for the opposite

perl

$s2 = ucfirst($s);

use lcfirst for the opposite - this is identical to php

Upper case first letter of each word - i.e. like excel proper()

php

$s2 = ucwords($s);

python

s2 = s.title()

Array construction

php

$a = array(1,2,3);

python

arr = [1,2,3]

perl

@arr = (1,2,3);

arrays can only be single dimensional, unless you use references

perlr

$arr_ref = [1,2,3];

perl

@arr = qw(cat dog fish);

unquoted, so no spaces

ruby

a = %w[cat dog fish]

unquoted, so no spaces

Array cloning

python

a2 = a[:]

non-scalers within array will be copied as references. Does the same thing as copy.copy()

python

import copy
a2 = copy.deepcopy(a)

non-scalers within array will be cloned as new objects

ruby

a2 = a.clone

non-scalers within array will be copied as references

Array referencing

Hash construction with values

php

$h = array('k'=>'v','k2'=>'v2');

perl

%h = ('k','v','k2','v2');

hashs can only be single dimensional, unless you use references

perlr

$h_ref = {k => 'v', k2 => 'v2'};

python

h = {'k':'v','k2':'v2'}

ruby

h = {'k'=>'v','k2'=>'v2'}

Hash add key / value

perl

$hash{$k} = $v;

use $hash rather then %hash, because the value you are refering to is a scalar

perlr

$hash->{$key};

Hash cloning

python

h2 = h.copy()

Hash referencing

Create a range

php

$a = range(0,5);

inclusive, i.e. 0,1,2,3,4,5

perl

@a = 1..5;

also works with letters i.e. a..j

ruby

r = 0..2 # 0,1,2
r = 0...2 # 0,1

a range in an object in ruby, not an array

Array push

php

array_push($a,$v);

python

arr.append(v)

Array pop

php

$v = array_pop($arr);

Array access last value

php

$v = $a[count($a)-1];

php

$v = end($a)

moves internal array pointer which may mess up looping

Array access single value

perlr

$v = $arr->[5];

Array access multiple values

perl

@a2 = @a[1,3];

returns 1 AND 3

python

a2 = a[1::2]

starting at 1, access every 2nd value

ruby

a2 = a[2..4]

return values 2 to 4 inclusive. can also been used to set values i.e. a[2..4] = [7,8,9]

ruby

a2 = a[2...4]

return values 2 to 4 exclusive

Array modify value

perl /* using $arr[5] because $v is a scaler, you don't use @arr[5] as you'd expect

$arr[5] = 10;

perlr

$arr->[5] = 10;

Value exists in array

php

$b = in_array($v,$a);

perl

$v = grep $_ eq $v, @arr

returns $v if it finds it (which will always be evaluated as 'true' even if $v is 0

perl

$v = grep $v, @a;

though didn't work when was looking up IP addy for key

ruby

b = a.include? v

Array comparison

Array length

perl

$n = scalar @a;

ruby

n = a.length

a.size is an alias

ruby

n = a.nitems

doesn't include nil values

Array sort

php

function _sort($a,$b) { return strcasecmp($a,$b); }
usort($a,'_sort');

sorts in place. _sort returns <0, 0 or >0;

php

usort($a, create_function('$a,$b','return strcasecmp($a,$b);'));

lamba style - however these don't get garbage collected so if this is in a look it'll create a mess

python

a.sort()

sorts in place

ruby

a.sort!

sort in place

ruby

a2 = a.sort {|x,y| a <=> b}

<=> is comparison operator, returns -1, 0, 1

Hash sort

php

ksort
uksort

see array sort

python

a = h.keys()
a.sort()
for k in a:
v = h[k]

hashes are naturally unordered in python

Key exists in hash

php

$b = isset($h[$k]);

perl

$b = defined $arr[$k];

python

b = a.has_key(k)

ruby

b = h.include? k

Hash keys

php

$a = array_keys($h);

Hash values

php

$a = array_values($h);

perl

$a = values %h;

String concatination

perl

$s = 'a' . 'b';

python

s = 'a' + 'b'

Charcode

String replace

php

$s = str_replace(match, replacement, $s);

python

s2 = s.replace(match, replacement)

Utf print

python

import codecs
sys.stdout = codecs.getwriter('utf')(sys.stdout) # sometimes you'll need this

Sprintf

php

$s = sprintf('The %s brown %s','quick','fox');

perl

$s = sprintf('The %s brown %s','quick','fox');

python /* can use a scaler instead of an tuple if only a single value */

s = 'The %s brown %s' % ('quick','fox')

String to array - split

php

$arr = preg_split("/$rx_delimeter/",$s);

php

$arr = split($delimeter,$s);

php

$arr = explode($delimeter,$s);

identical to split?

perl

@a = split /$rx/, $s;

can also just use $s instead of /$rx/

Array to string - join

php

$s = implode($glue, $a);

python

s = ''.join(a)

Regular expression match

php

$b = preg_match("/$rx/",$s);

can use other delimiters

php

preg_match_all("/$rx/",$s,$matches);

will save details of matches to array $matches

perl

$b = $s =~ /$rx/;

perl

$b = $s =~ m{$rx}; # or () <> || ## etc
$s = 'abc';
$rx = 'b';
$rx2 = 'd';
$res = $s =~ m{$rx} and not $s =~ m($rx2);

allows different delimiters including braces + brakets. standard // is actually just a shortcut for m//

ruby

n = s =~ /rx/

returns the character offset of match, nil if no match

ruby

n = s =~ /#{rx}/

dynamic

Regular expression replace

php

$s = preg_replace("/$rx/",$replacement,$s);

perl

$s =~ s/$rx/$replacement/g;

python

import re
$s = re.sub(rx,replacment,s)

make rx strings with "r" i.e. r'c:\user'. use matches in replacement like r'\1hello\2'

Array slice

php /* unknown */

$a = array_slice()

perl

@a2 = @a[1..3];

returns 1 TO 3

python

a2 = a[1:3]

returns 1 TO 2, i.e. 1 - (not including) 3

Array reverse

php

$a2 = array_reverse($a);

perl

@a2 = reverse @a;

python

a.reverse()

reserves in place

Iterate line by line over a text file

php

$fh = fopen('data.txt');
while ($line = fgets($fh)) {
$line = preg_replace('/[\r\n]/','',$line);
}
fclose($fh);

php

$s = file_get_contents('data.txt');
$arr = preg_split('/\n/',$s);
foreach ($arr as $line) ...

will read entire file into memory first

perl

open FH, 'data.txt';
for $line (<FH>) {
chomp $line;
}
close FH;

or can for (<FH>) and $line = $_

python

sys.stdout = codecs.getwriter('utf')(sys.stdout) # so that you can use the 'print' fn
import codecs
fh = codecs.open(filename,'r','latin-1')
for line in fh:

in python its critical that you use codecs to open files so that any non ascii characters get happily encoded in unicode /* i think */

python

fh = open(filename,'r')
for line in fh:

will result in a string object rather then a unicode object. this can cause big headaches if it includes non ascii characters /* i think */

Write to a file

php

$fh = fopen('out.txt','w');
fwrite($fh,$s);
fclose($fh);

perl

open FH, '>out.txt';
print FH "Hello world\n";
close FH;

use > for write, >> for append

python

f = open('out.txt', 'w')
f.write(s)
f.close()

Read contents from an external website

php

$s = file_get_contents($url);

download a library that implements cURL for anything more advanced using HTTP

python

import httplib
conn = httplib.HTTPConnection('www.somewhere.net.nz')
conn.request("GET", "/documents/index.html")
xhtml = conn.getresponse().read()

Call a system command, get output

php

ob_start();
system($command);
$s = ob_get_clean();
print $s;

Get arguments after calling from command line

perl

@ARGV;

refer to them as $ARGV[0] etc

Cgi - get

Cgi - post

php

$h = $_POST;

there's also a way to get raw post, something like apache_request_headers(':/POST');

While loop

php /* don't think that it uses the word 'do' anywhere */

while ($b) {}

Do loop

perl

do {} while ($b);

Switch statement

php

switch ($var) {
case 'one': // is in $var == 'one'
default:
}

*i think*

Continue, break

php

foreach ($a as $v) {
if ($b) continue;
# do whatever
}

break acts exactly the same

perl

NAMED_LINE: for ($i=0;$i<scalar(@a); $i+=1) {
next NAMED_LINE if ($i >= 5);
}

Equivalent of continue, not sure what to do for break

python

for i in range(len(a)):
if i >= 5: continue

break acts exactly the same

Else if

php

else if
elseif

either is fine

Deleting varaiables

Print_r, var_dump

php

print_r($arr);
var_dump($var);

perl

use Data::Dumper;
print Dumper \$var;

perl

use Data::Dumper;
sub p { print $_[0].chr(10); }
sub d { print Dumper @_; }

Mysql datetime to timestamp - 2008-10-14 12:00:04

php

$val = explode(" ",$datetime);
$date = explode("-",$val[0]);
$time = explode(":",$val[1]);
$timestamp = mktime($time[0],$time[1],$time[2],$date[1],$date[2],$date[0]);

Open a mysql database connection

php

$db = mysql_connect($host,$username,$password);
mysql_select_db($database);

python

import MySQLdb, MySQLdb.cursors
db_connection = MySQLdb.connect(user=username, passwd=password, db=database , cursorclass=MySQLdb.cursors.DictCursor)
db = db_connection.cursor()

db.close() at end of script

Mysql query return assoc

php

$result = mysql_query($sql);
while ($row = mysql_assoc($result))

python

db.execute(sql)
db.fetchall()

python

db.execute(sql)
db.fetchone()

Mysql insert

php

mysql_query($sql);

python

db.execute(sql)
db_connection.commit()

Die / exit

php /* i think */

exit($s);

python

import sys
sys.exit()

Loop a filesystem directory

perl

sub loop_dir_recursive {
my ($dir) = $_[0];
for my $filepath(<$dir/*>) {
$filename = $filepath;
$filename =~ s|^.*/(.*)$|$1|g; # switch slash around for windows
if (-d $filepath) {
# is a directory
loop_dir_recursive($filepath);
} elsif (-f $filepath) {
# is a file
} else {
# is something else ie symlink
}
}
}

Recursively copy a directory with file filter

perl

use File::Copy 'cp';
use File::Path 'mkpath';
sub copy_files_recursive {
my ($dir) = @_;
for my $filepath (<$dir/*>) {
if (-d $filepath) {
next if ($filepath =~ m!(output|rips)!);
copy_files_recursive($filepath);
} elsif (-f $filepath) {
if ($filepath =~ m!\.(png|gif|jpg)$!) {
$target_filepath = 'output/test/' . $filepath;
$target_path = $target_filepath;
$target_path =~ s!/[^/]*?$!!g;
if (not -e $target_path) {
mkpath($target_path) or die ("$!");
print "Creating $target_path".chr(10);
}
print "Copying $filepath -> $target_filepath".chr(10);
cp $filepath, $target_filepath or die ("$!");;
}
} else {
# is something else ie symlink
}
}
}

Class

php

class MyClass extends MyParent {
var $my_var = 15;
function MyClass($arg) { // constructor - __construct for php5 ??
$this->MyParent($arg); // super
}
}

python

class MyClass(MyParent):
my_var = 15
def __init__(self): # constructor
self.my_other_var = 17

ruby

class Child < Parent
my_var :my_val
attr_accessor :instance_var # writes getter + setter
def initialize(v)
@instance_var = v
end
def self.class_method
end
protected
def pro
end
private
def priv
end
end

Construct object

php

$my_obj = new MyClass($arg);

python

my_obj = MyClass(arg)

Dynamic variable

Dynamic function

php

call_user_func($fn,$args);

Import

php

require()
require_once()
include()
include_once

require will throw an error of some kind - *i think* that saying _once() means that it won't import if asked to import multiple times, so no need to check if a class already exists

perl

use Data::Dumper;

this uses stuff from CPAN etc, think there's a different syntax for getting stuff that's local and relative to .pl file

Contents

What variables mean

php | perl | perlr | python

Booleans

php

perl

python

ruby

Null + other

php

perl

python

ruby

Division

php

python

ruby

Numeric power

php

perl

python

python

ruby

Mod

php

python

ruby

For loop over an array

php

php

php

perl

perl

python

python

ruby

ruby

ruby

javascript

For loop over a hash

php

php

php

perl

perl

python

ruby

javascript

Statement modifiers slash tenary operators

php

perl

python

ruby

Scalar construction

php

perl

python

ruby

javascript

Scalar referencing

php

perl

Scalar cloning

php

perl

python

ruby

Trim

python

php

perl

Upper case string

php

python

perl

Lower case strimg

php

python

perl

Upper case first letter of a string