PHP for Python Developers

SEMANTIC WEAPONS
PHP Conf 2016
HELLO STRANGER

SEMANTIC WEAPONS
$ id -un
– carlos@semantic.mx
– tweet me @cvences
– Founded a 4yo development shop
– semanticweapons.com
#phpconmx

and we’re hiring!
HELLO STRANGER
SEMANTIC WEAPONS

SEMANTIC WEAPONS
PHP for Python Developers

SEMANTIC WEAPONS
PHP for Python Developers
Web Development & General Scripting

SEMANTIC WEAPONS
$ membership operator _
$inArray = in_array(5, range(0, 10)) === TRUE;

SEMANTIC WEAPONS
in_array = 5 in range(10) == True

SEMANTIC WEAPONS
in_array = 5 in range(10) == True
>>> in_array
False

SEMANTIC WEAPONS
$ default values _
# counting dictionary keys
from collections import defaultdict
log = ['warn', 'error', 'debug', 'info', 'warn', 'debug', 'warn']
stats = defaultdict(int)
for entry in log:
stats[entry] += 1

SEMANTIC WEAPONS
$ default values _
// counting elements
$log = ['warn', 'error', 'debug', 'info', 'warn', 'debug', ‘warn'];
$stats = [];
foreach ($log as $entry){
$stats[$entry] = $stats[$entry]++ ?: 0;
}

SEMANTIC WEAPONS
$ default values _
$stats = [];
$stats[$entry]++;
}

SEMANTIC WEAPONS
$ default values _
$stats = [];
$stats[$entry]++;
}
# counting dictionary keys
from collections import defaultdict
log = ['warn', 'error', 'debug', 'info', 'warn', 'debug', ‘warn']
stats = defaultdict(int)
for entry in log:
stats[entry] += 1

SEMANTIC WEAPONS
Memory consumption
– C’s pointers
– SQL’s LIMIT statement
– strcmp, strcpy, strcat
– strncmp, strncpy, strncat
– buffer overflow

SEMANTIC WEAPONS
Memory consumption
– C’s pointers
– SQL’s LIMIT statement
– strcmp, strcpy, strcat
– strncmp, strncpy, strncat
– buffer overflow
¿Quién agregó
la clausula LIMIT
a mini SQL 1.x?

SEMANTIC WEAPONS
$ Array
function myRange($max = 10) {
$numeros = [];
$num = 1;
while ($num < $max) {
array_push($numeros, $num);
$num++;
}
return $numeros;
}
function sum($max = 10) {
$sumatoria = 0;
foreach (myRange($max) as $num) {
$sumatoria += $num;
}
echo $sumatoria;
}
sum(1000000);

SEMANTIC WEAPONS
$ Iterator
class NumberIter implements Iterator {
private $position = 0;
private $array = [];
public function __construct($array = []) {
$this->position = 0;
$this->array = $array;
}
public function rewind() {
}
public function current() {
return $this->array[$this->position];
}
public function key() {
return $this->position;
}
public function next() {
++$this->position;
}
public function valid() {
return isset($this->array[$this->position]);
}
}
$sumatoria = 0;
$numberIter = new NumberIter($array = range(1, ($max - 1)));
foreach ($numberIter as $num) {
$sumatoria += $num;
}
echo $sumatoria;
}
sum(1000000);

SEMANTIC WEAPONS
$ PHP Arrays vs Iterators
$sumatoria += $num;
}
foreach ($numberIter as $num) {
$sumatoria += $num;
}

SEMANTIC WEAPONS
Entering
Generators

SEMANTIC WEAPONS
$ Generators
// $numeros = [];
$num = 1;
yield $num;
$num++;
}
// return $numeros;
}
$sumatoria = 0;
$sumatoria += $num;
}
echo $sumatoria;
}
sum(1000000);

SEMANTIC WEAPONS
Generators
– Implement Iterators
– DRY
– Can traverse with foreach
– foreach does not use IAP (>7.0.0)
– Uses hashtable iterators now
– Does not build an array in-memory
– Also speeds time to generate
Note: – Calling range(0, 1000000) will result in well over 100 MB of memory being used.

SEMANTIC WEAPONS
$ Iterators, Generators and Arrays
}
}
}
}
++$this->position;
}
}
}
$num = 1;
yield $num;
$num++;
}
}
array range ($start, $end, $step)

SEMANTIC WEAPONS
$ Iterators, Generators and Arrays
}
}
}
}
++$this->position;
}
}
}
$num = 1;
yield $num;
$num++;
}
}

SEMANTIC WEAPONS
Case of Study

SEMANTIC WEAPONS
$ PHP 7.1.0 RC2_

SEMANTIC WEAPONS
Using Generators

SEMANTIC WEAPONS
Using Iterators

SEMANTIC WEAPONS
HELLO STRANGER
PHP 7.1.0 RC2

SEMANTIC WEAPONS
To be or not to be
– Using iterators is great
– foreach in 7.0.0 rocks!
– lists are fat, sequences evaluate lazily
– Lazy is good

SEMANTIC WEAPONS
Warning: sort() expects parameter 1 to be array, object given

SEMANTIC WEAPONS
But…
– Python iterators introduced in 2.2 (2001)
– range -> xrange -> range
– PHP yield introduced in 5.5.0+ (2013)
– Iterator name space may clash
– What’s wrong with iterator_to_array?
– PHP ArrayAccess
Blog Post: SPL Iterators against the performance
PHP Manual: /language.generators.overview.php

SEMANTIC WEAPONS
$ unpacking a list _
sum_of_numbers = sum([x**3 for x in range(10000)])

SEMANTIC WEAPONS
$ unpacking an array _
$sumOfNumbers = 0;
foreach (range(1, 10000) as $num) {
$sumOfNumbers += pow($num, 3);
}

SEMANTIC WEAPONS
// second try
$processArray = function($method, $array) {
return array_map($method, $array);
};
$sumOfNumbers = array_sum(
$processArray(
$method = function($x){return pow($x, 3);},
$array = range(0, 10000)
)
);

SEMANTIC WEAPONS
One liners
– means something in English
– easy to understand at first glance

SEMANTIC WEAPONS
$sumOfNumbers = 0;
foreach (range(1, 10000) as $value) {
$sumOfNumbers += pow($value, 3);
}
// second try
$processArray = function($method, $array) {
return array_map($method, $array);
};
$sumOfNumbers = array_sum(
$processArray(
$method = function($x){return pow($x, 3);},
$array = range(0, 10000)
)
);
// third try
$sumOfNumbers = array_sum(array_map(function($x){return pow($x, 3);}, range(0, 10000)));

SEMANTIC WEAPONS
$ readability _
sum_of_numbers = sum([x**3 for x in range(10000)])
$y = array_sum(array_map(function($x){return pow($x, 3);}, range(0, 10000)));

SEMANTIC WEAPONS
$ looping over two collections _
speakers = ['Javier', 'Joe', 'Rasmus', 'Carlos']
talks = ['Ansible', 'Loopless', 'Deploy', 'Python']
for speaker, talk in zip(speakers, talks):
print(speaker, talk)

SEMANTIC WEAPONS
$speakers = ['Javier', 'Joe', 'Rasmus', 'Carlos'];
$talks = ['Ansible', 'Loopless', 'Deploy', 'Python'];
$max = min(count($speakers), count($talks));
foreach(range(0, $max-1) as $i){
echo($speakers[$i] .' '. $talks[$i]);
}

SEMANTIC WEAPONS
// second approach
$speakers = ['Javier', 'Joe', 'Rasmus', 'Carlos'];
$talks = ['Ansible', 'Loopless', 'Deploy', 'Python'];
$meetupTalks = array_combine($speakers, $talks);
foreach($meetupTalks as $speaker => $talk){
echo "$speaker $talk";
}

SEMANTIC WEAPONS
for speaker, talk in zip(speakers, talks):
print(speaker, talk)
foreach(array_combine($speakers, $talks) as $speaker => $talk)
echo "$speaker $talk";

SEMANTIC WEAPONS
$ python iterators magic, tweet .@cvences
# dado un array asociativo, elimina todos los nombres que empiecen con la letra “c” 
meetup_info = { 
'Javier': 'Ansible', 
'Joe': 'Loopsless', 
'Rasmus': 'Deploy', 
'Carlos': 'Python', 
} 
 
meetup_info = {key: meetup_info[key] for key in meetup_info if not key.lower().startswith('c')}
# dado un modelo con relationships, filtra los blogs cuyos autores tengan o no
# un nombre asignado. El título no incluye la palabra python y ordénalos por fecha
# de creación descendente.
 
Blog.objects
.filter(entry__authors__isnull=False, entry__authors__name__isnull=True)
.exclude(entry__title__icontains=‘python’)
.order_by(‘-created’)

SEMANTIC WEAPONS
$ python iterators magic
def fib(n): 
return (4 << n * (3 + n)) // ((4 << 2 * n) - (2 << n) - 1) & ((2 << n) - 1)
def get_fibonacci_by_position(pos): 
""" 
Returns the fibonacci number at pos 
 
""" 
a, b = 1, 1 
 
for _ in range(pos): 
a, b = a + b, a 
 
return b

carlos@semantic.mx
HELLO STRANGER
SEMANTIC WEAPONS

PHP for Python Developers

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