DEV Community: Burak Ibis

Using Python Enum and IntEnum Like An Expert

Burak Ibis — Tue, 31 Mar 2020 21:11:22 +0000

Hello guys. If you use forms on your Django web applications and you want to clean model scheme, you should use enums!

Let's start

For example, you have a product model and your visitors select something on form like status.

We consider the options as follows:

Task
Pending
Published

...you have a two option. First one is complex and unmanagable.
You can create tuple like below and add 'choises' attribution to CharField:

STATUS = (
  ("TASK", "Task"),
  ("PENDING", "Pending"),
  ("PUBLISHED", "Published"),
)

STATUS = (
  (1, "TASK"),
  (2, "PENDING"),
  (3, "PUBLISHED"),
)

Your product model:

class Product(models.Model):
  category = models.ForeignKey("Category", on_delete=models.CASCADE,
    verbose_name="Category Name", blank=True, null=True)
  title = models.CharField(max_length=50, verbose_name="Product Title",
    blank=True, null=True)
  status = models.CharField(choices=STATUS)

It is correct and will work without errors. Python will save them to db as string.
But it is both complex and unmanageable. Because If you want to use this field anywhere, you need to call like below because tuple is not useful for calling:

def example(self):
  if self.status == 1:
    make_something()
  elif self.status == 2:
    make_something()

I prefer using Enum or IntEnum.
Firstyl we need import Enum:

from enum import Enum, IntEnum

Let's create our enum classes. Don't worry, we don't need create new migrations.

class Status(enum.Enum):
  TASK = "Task"
  PENDING = "Pending"
  PUBLISHED = "Published"

or (how you want to keep them)

class Status(enum.IntEnum):
  TASK = 1
  PENDING = 2
  PUBLISHED = 3

And your model should be below:

class Product(models.Model):
  ...
  status = models.CharField(
    choices=(
        (x.value, x.name.title()) for x in Status),
    default=Status.TASK
    )

class Product(models.Model):
  ...
  status = models.IntegerField(
    choices=(
        (x.value, x.name.title()) for x in Status),
    default=Status.TASK
    )

You can set a default value as I added above.
How do you use Enum on functions or anywhere?

You will call enums like below:

def example(self):
  if self.status == Status.TASK.value:
    make_something()
  elif self.status == Status.PUBLISHED.value:
    make_something()

or you can iterate them like below:

def get_states(self):
  return [{"id": s.id, "name": s.name} for s in Status]

Congratz! It's Pythonic way.

Hello Little Arduino!

Burak Ibis — Sun, 08 Dec 2019 15:26:16 +0000

Hello everyone! My company is based of software development but also our another team is education based. We are giving robotic coding education to elementary/highscools. We have a website that has a lot of lessons about robotics and 3D printers. We are redesigning this site and I am part of this. When I looking to site I wondered how these boards working, what kind of things can making with that. I searched on Google, I was little bit confused so finally I got all of ingredients from our office and start this post. Let's make 'a homemade light switch' together and see how do it works.
I will use Fedora but you can use any Linux distros, Windows or MacOs.

Ingredients For Your Homemade Light Switch

Arduino UNO with USB port
Arduino IDE
OpenJDK
Git (It's not neccessary)
An Internet connection
“Root” access to the development machine
Node.js
Johnny-Five and narf

Let's Start

Install Arduino IDE from https://www.arduino.cc/en/main/software, select your OS, download file and setup or install from command line sudo dnf install arduino
Install openJDK from https://jdk.java.net/13/ or from command line: sudo dnf install java-11-openjdk.x86_64 (for detecting your Arduino Card).
Plug the board to your computer with USB TTL serial cable (USB-A to USB-B).
Let's check our device that connect to our PC correctly:
Our command is: dmesg | tail It will be list our all of connections. If you see like below output:

[fedora@localhost ~]$ dmesg | tail
[  144.148444] atkbd serio0: Use 'setkeycodes e02b <keycode>' to make it known.
[ 1079.091148] usb 1-1: USB disconnect, device number 5
[ 1079.092304] ch341-uart ttyUSB0: ch341-uart converter now disconnected from ttyUSB0
[ 1079.092381] ch341 1-1:1.0: device disconnected
[ 1081.563604] usb 1-1: new full-speed USB device number 7 using xhci_hcd
[ 1081.691846] usb 1-1: New USB device found, idVendor=1a86, idProduct=7523, bcdDevice= 2.54
[ 1081.691856] usb 1-1: New USB device strings: Mfr=0, Product=2, SerialNumber=0
[ 1081.691862] usb 1-1: Product: USB2.0-Serial
[ 1081.694861] ch341 1-1:1.0: ch341-uart converter detected
[ 1081.695788] usb 1-1: ch341-uart converter now attached to ttyUSB0

If you see something like this, congratulations! You device connected successfuly.

Set up project workspace:
You will need to create and set up a project workspace for creating the Arduino application. For our project, we will be using Node.js as the language for creating the switch. There are several ways to create this kind of application, It doesn't matter, you can use any language for this, but to help get you started, I created an HTML page and the JavaScript file you can use for your own set up.
You can find my demo code available on GitLab. For this project, you will want a copy of the index.html and connectArduino.js files. You can copy and paste the two files into the project workspace you created earlier.
GitLab Project: https://gitlab.com/burakibis/hello-little-arduino
Setting up Node.js
Now that we have our workspace and files needed for running the project, we will need to set up a Node.js server to run the application. To begin with running the “light switch server”, you will need to install Node.js and NPM, the package manager for Node.js applications.
Enter the following commands to install the necessary dependencies with Node package manager:
For installing Node.js:

sudo dnf install npm nodejs

For building JSON API with Javscript:

npm install narf

For connection to our Arduino board:

npm install serialport

We need robotics framework for coding our board. We will use Johnny Five. Johnny-Five is an Open Source, Firmata Protocol based, IoT and Robotics programming framework, developed at Bocoup. Johnny-Five programs can be written for Arduino (all models), Electric Imp, Beagle Bone, Intel Galileo & Edison, Linino One, Pinoccio, pcDuino3, Raspberry Pi, Particle/Spark Core & Photon, Tessel 2, TI Launchpad and more!

npm install johnny-five

For install all of dependencies:

npm install

Some of dependecies were changed and won't work correctly, so you can get a error like these:

home/burak/Arduino/projects/hello-little-arduino/node_modules/pageserver/lib/pageserver.js:97
                    var type = mime.lookup(filepath);
                                    ^

TypeError: mime.lookup is not a function
    at /home/burak/Arduino/projects/hello-little-arduino/node_modules/pageserver/lib/pageserver.js:97:37
    at suppressedCallback (fs.js:199:5)
    at FSReqWrap.args [as oncomplete] (fs.js:140:20)

Don't worry!. We just fix a file on YOUR_PATH/hello-little-arduino/node_modules/pageserver/lib/pageserver.js:97
In the new version of mime renamed some methods so we should go to file and change this line
var type = mime.lookup(filepath); to var type = mime.getType(filepath);
Save and close this file.

FINAL

So we are ready for run our project! Let's do it: run node connectArduino.js on console and write
http://127.0.0.1:8079/index.html to your browser.
TADA! You will see two button (On-Off). Click someone and look at your board's lights. Ehm.. You are awesome robotic programmer bro. Do more!

You can read this article and more on my tech blog: https://virgul.co

Cover Photo by Rock'n Roll Monkey on Unsplash