metal3d

# Why DI Framework are useful

Dependency injection is back in fashion. That's probably the result AngularJS, Symfony2, and many Java frameworks success that offer a "DI" implementation. But what is "DI", and why are we able to *not use* "DI" framework with Python ?

## What is dependency injection

Dependency injection is a pattern, or it is rather a way to implement dependencies between classes. The approach is basically to avoid classes to directly instanciate objects, and make use of interfaces and/or factories. That's all, nothing more complicated.

To illustrate the definition, it's simpler to look at an example. 

metal3d

/* To put in ~/.config/gtk-3.0/gtk.css */
/* Create directory and file if they don't exist */
/* Change paddings to fill your preferences */
.header-bar.default-decoration {
    padding-top: 1px;
    padding-bottom: 1px;
}
.header-bar.default-decoration .button.titlebutton {
    padding-top: 1px;
    padding-bottom: 1px;

metal3d

diff -up ./deploy_coreos_libvirt.sh.friend ./deploy_coreos_libvirt.sh
diff -up ./deploy_coreos_libvirt.sh.friend ./deploy_coreos_libvirt.sh
--- ./deploy_coreos_libvirt.sh.friend   2016-01-25 14:18:15.431503583 +0100
+++ ./deploy_coreos_libvirt.sh  2016-01-25 14:24:35.942741966 +0100
@@ -51,6 +51,12 @@ for SEQ in $(seq 1 $1); do

         sed "s#%HOSTNAME%#$COREOS_HOSTNAME#g;s#%DISCOVERY%#$ETCD_DISCOVERY#g" $USER_DATA_TEMPLATE > $LIBVIRT_PATH/$COREOS_HOSTNAME/openstack/latest/user_data

+
+        if [[ selinuxenabled ]] ;then

metal3d

Python et l'injection de dépendance

Ah, ça... quand on parle d'injection et de dépendance, on s'attend tout de suite à se prendre une flopée de visiteurs en manque de substance plus ou moins illicites. En réalité, on va parler "pattern". Et surtout, je vais lancer un vieux pavé dans la marre en disant qu'en Python c'est pas super utile, ou du moins que le langage permet déjà de le gérer sans se faire mal.

Piqure de rappel

Conversation un matin au travail:

metal3d

package main

import (
	"encoding/json"
	"flag"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"os"

metal3d

import requests
import json
import sys
 
# use argv... example:
# python github-dl-count MyUserName MyRepoName
user = sys.argv[1]
repo = sys.argv[2]
 
url="https://api.github.com/repos/%s/%s/releases" % (user, repo)

metal3d

# -*- encoding: utf-8 -*-
""" threadpool module, export ThreadPool class that is a non blocking
Thread Queue. Most important is that ThreadPool.add_task runs
asychroniousally. This method doesn't block process.

Example:
    p = ThreadPool(2)
    p.add_task(f1, arg1, arg2, test=False)
    p.add_task(f1, arg2, arg3, test=False)
    p.add_task(f1, arg4, arg5, test=True)

metal3d

# -*- encoding: utf-8 -*-
""" Simple Bayesian calculation

After training datas by categories, you can use Bayes.bayes method to compute
bayesian calculation to find probality for a content
matches some categories

Example:

>>> b = Bayes()

metal3d

@startuml
A -> B: le label de mon appel
B -> A: autre label...
@enduml

metal3d

/*
NAT traversal system to let 2 computers behind firewall to communicate.

Example:
Client A (your machine) has public ip 1.1.1.1
Client B (distant machine) has public ip 2.2.2.2

You want to bind port 5556 on your machine
Distant Client want to bind port 5557