Python 3.8.2 : Create a Django Calendar - part 002.

I was a bit busy with another project I am working on and this is the reason that led to the delay of this tutorial.

The big problem with Django tutorials is the volume of the source code.

Because of this, this tutorial will highlight changes to the source code and share it in my GitHub account.

Let's see the changes into my project tree and files:

└───test_calendar
    ├───first_calendar
    │   ├───migrations
    │   └───static
    │       └───first_calendar
    │           └───css
    ├───media
    ├───templates
    └───test_calendar

The settings.py file:

...
INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'first_calendar.apps.FirstCalendarConfig',
]
...
# Static files (CSS, JavaScript, Images)
# https://docs.djangoproject.com/en/2.0/howto/static-files/

STATICFILES_DIRS = [
    os.path.join(BASE_DIR, '/static/')
]

STATIC_ROOT = os.path.join(BASE_DIR, 'static')
STATIC_URL = '/static/'

MEDIA_ROOT = os.path.join(BASE_DIR, 'media')
MEDIA_URL = '/media/'

The complete project is a basic calendar, which can be modified by adding events or linked to a Google calendar.

The source code can be found here.

Python 3.8.2 : Create a Django Calendar - part 001.

This tutorial show you how can use pipenv tool and set the Django project in order to create a calendar with Django project.

First, install the pipenv tool using the pip tool:

python -m pip install pipenv
Collecting pipenv
...
Successfully installed pipenv-2020.6.2 virtualenv-clone-0.5.4

You can see all options and features with this command:

pipenv
Usage: pipenv [OPTIONS] COMMAND [ARGS]...

Options:
  --where                         Output project home information.
  --venv                          Output virtualenv information.
  --py                            Output Python interpreter information.
  --envs                          Output Environment Variable options.
  --rm                            Remove the virtualenv.
  --bare                          Minimal output.
  --completion                    Output completion (to be executed by the
                                  shell).

  --man                           Display manpage.
  --support                       Output diagnostic information for use in
                                  GitHub issues.

  --site-packages / --no-site-packages
                                  Enable site-packages for the virtualenv.
                                  [env var: PIPENV_SITE_PACKAGES]

  --python TEXT                   Specify which version of Python virtualenv
                                  should use.

  --three / --two                 Use Python 3/2 when creating virtualenv.
  --clear                         Clears caches (pipenv, pip, and pip-tools).
                                  [env var: PIPENV_CLEAR]

  -v, --verbose                   Verbose mode.
  --pypi-mirror TEXT              Specify a PyPI mirror.
  --version                       Show the version and exit.
  -h, --help                      Show this message and exit.


Usage Examples:
   Create a new project using Python 3.7, specifically:
   $ pipenv --python 3.7

   Remove project virtualenv (inferred from current directory):
   $ pipenv --rm

   Install all dependencies for a project (including dev):
   $ pipenv install --dev

   Create a lockfile containing pre-releases:
   $ pipenv lock --pre

   Show a graph of your installed dependencies:
   $ pipenv graph

   Check your installed dependencies for security vulnerabilities:
   $ pipenv check

   Install a local setup.py into your virtual environment/Pipfile:
   $ pipenv install -e .

   Use a lower-level pip command:
   $ pipenv run pip freeze

Commands:
  check      Checks for PyUp Safety security vulnerabilities and against PEP
             508 markers provided in Pipfile.

  clean      Uninstalls all packages not specified in Pipfile.lock.
  graph      Displays currently-installed dependency graph information.
  install    Installs provided packages and adds them to Pipfile, or (if no
             packages are given), installs all packages from Pipfile.

  lock       Generates Pipfile.lock.
  open       View a given module in your editor.
  run        Spawns a command installed into the virtualenv.
  shell      Spawns a shell within the virtualenv.
  sync       Installs all packages specified in Pipfile.lock.
  uninstall  Uninstalls a provided package and removes it from Pipfile.
  update     Runs lock, then sync.

Create a folder for your project, I used this folder named django_test_002:

mkdir django_test_002

Create a virtualenv using the pipenv shell

django_test_002>pipenv shell
Creating a virtualenv for this project…
Pipfile: D:\Projects\Python\django_test_002\Pipfile
Using D:/Python38/python.exe (3.8.2) to create virtualenv…
...

Install Django python package:

(django_test_002-bp-hUvnN) D:\Projects\Python\django_test_002> pipenv install Django
Installing Django…
Adding Django to Pipfile's [packages]…
Installation Succeeded
Pipfile.lock not found, creating…
Locking [dev-packages] dependencies…
Locking [packages] dependencies…
 Locking...Building requirements...
Resolving dependencies...
Success!
Updated Pipfile.lock (a6086c)!
Installing dependencies from Pipfile.lock (a6086c)…
  ================================ 0/0 - 00:00:00

Let's test the pipenv shell tool with a simple example for activate, deactivate and exit:

D:\Projects\Python\django_test_002>pipenv shell
Launching subshell in virtual environment…
Microsoft Windows [Version 10.0.18363.900]
(c) 2019 Microsoft Corporation. All rights reserved.

(django_test_002-bp-hUvnN) D:\Projects\Python\django_test_002>activate

(django_test_002) (django_test_002-bp-hUvnN) D:\Projects\Python\django_test_002>deactivate
(django_test_002-bp-hUvnN) D:\Projects\Python\django_test_002>exit

Stores all the python packages you installed into a requirements.txt file

D:\Projects\Python\django_test_002>pipenv shell
Launching subshell in virtual environment…
Microsoft Windows [Version 10.0.18363.900]
(c) 2019 Microsoft Corporation. All rights reserved.

(django_test_002-bp-hUvnN) D:\Projects\Python\django_test_002>pip3 freeze > requirements.txt

Create django project named test_calendar:

(django_test_002-bp-hUvnN) D:\Projects\Python\django_test_002>django-admin startproject test_calendar

Start server to check that our project is running at localhost:8000.

(django_test_002-bp-hUvnN) D:\Projects\Python\django_test_002>cd test_calendar

(django_test_002-bp-hUvnN) D:\Projects\Python\django_test_002\test_calendar>python manage.py runserver
Watching for file changes with StatReloader
Performing system checks...

System check identified no issues (0 silenced).

You have 17 unapplied migration(s). Your project may not work properly until you apply the migrations 
for app(s): admin, auth, contenttypes, sessions.
Run 'python manage.py migrate' to apply them.
June 13, 2020 - 20:52:00
Django version 3.0.7, using settings 'test_calendar.settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CTRL-BREAK.

Now, you can open with your browser the default link http://127.0.0.1:8000/ and you will see the start page of Django framework.

Use Ctrl+C keys to stop it, and create an application.

I used the next command to create first_calendar application.

D:\Projects\Python\django_test_002\test_calendar>python manage.py startapp first_calendar

Into the folder application first_calendar make these changes to views.py from to create a index view:

from django.shortcuts import render
from django.http import HttpResponse

# Create your views here.

def index(request):
    return HttpResponse('hello')

Create a new file named urls.py in the folder first_calendar and add this source code:

from django.conf.urls import url
from . import views

app_name = 'first_calendar'
urlpatterns = [
    #url(r'^index/$', views.index, name='index'),
    url('', views.index,  name='index'),
]

Return to the project base folder and add the view to urls.py from the project test_calendar folder:

from django.contrib import admin
from django.urls import path, include

urlpatterns = [
    path('admin/', admin.site.urls),
    path('', include('first_calendar.urls')),
]

Into the project folder test_calendar add the application to the file settings.py.

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'first_calendar',
]

Use migrate option to migrate the project:

(django_test_002-bp-hUvnN) D:\Projects\Python\django_test_002\test_calendar>python manage.py migrate
Operations to perform:
  Apply all migrations: admin, auth, contenttypes, sessions
Running migrations:
  Applying contenttypes.0001_initial... OK
  Applying auth.0001_initial... OK
  Applying admin.0001_initial... OK
  Applying admin.0002_logentry_remove_auto_add... OK
  Applying admin.0003_logentry_add_action_flag_choices... OK
  Applying contenttypes.0002_remove_content_type_name... OK
  Applying auth.0002_alter_permission_name_max_length... OK
  Applying auth.0003_alter_user_email_max_length... OK
  Applying auth.0004_alter_user_username_opts... OK
  Applying auth.0005_alter_user_last_login_null... OK
  Applying auth.0006_require_contenttypes_0002... OK
  Applying auth.0007_alter_validators_add_error_messages... OK
  Applying auth.0008_alter_user_username_max_length... OK
  Applying auth.0009_alter_user_last_name_max_length... OK
  Applying auth.0010_alter_group_name_max_length... OK
  Applying auth.0011_update_proxy_permissions... OK
  Applying sessions.0001_initial... OK

Go back to default project folder. Now you can test using this command:

(django_test_002-bp-hUvnN) D:\Projects\Python\django_test_002\test_calendar>python manage.py runserver
Watching for file changes with StatReloader
Performing system checks...

System check identified no issues (0 silenced).
June 13, 2020 - 21:52:42
Django version 3.0.7, using settings 'test_calendar.settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CTRL-BREAK.

You will see a simple word: hello. Let's fix the admin login by adding user:

python manage.py createsuperuser
Username (leave blank to use 'catal'): catafest
Email address: catafest@yahoo.com
Password:

I set user catafest and password admin76 and then use the next command to see the result on http://127.0.0.1:8000/admin:

python manage.py runserver

The next step is to create a Event class into models.py file from first_calendar:

from django.db import models

class Event(models.Model):
    title = models.CharField(max_length=200)
    description = models.TextField()
    start_time = models.DateTimeField()
    end_time = models.DateTimeField()

Then add this class into admin.py file:

from django.contrib import admin
from first_calendar.models import Event

admin.site.register(Event)

This tutorial set the one default Django project with the Django framework version 3.0.7 .

Python 3.8.3 : Using the fabric python module - part 002.

This is second tutorial about the fabric.

Using the old example, I will show you how can use it with some basic features.

The example cover these issues:

• show fabric version;
• use task decorator;
• import and use multiple hosts;

The documentation page come with this info about task:

Fabric 1.1 introduced the Task class to facilitate new features and enable some programming best practices, specifically:

  Object-oriented tasks. Inheritance and all that comes with it can make for much more sensible code reuse than passing around simple function objects. The classic style of task declaration didn’t entirely rule this out, but it also didn’t make it terribly easy.

  Namespaces. Having an explicit method of declaring tasks makes it easier to set up recursive namespaces without e.g. polluting your task list with the contents of Python’s os module (which would show up as valid “tasks” under the classic methodology.)

With the introduction of Task, there are two ways to set up new tasks:

 Decorate a regular module level function with @task, which transparently wraps the function in a Task subclass. The function name will be used as the task name when invoking.

 Subclass Task (Task itself is intended to be abstract), define a run method, and instantiate your subclass at module level. Instances’ name attributes are used as the task name; if omitted the instance’s variable name will be used instead.

Let's see the example:

import fabric
from fabric import Connection
print("fabric.__version__")
print(fabric.__version__)

print("fabric.__version_info__")
print(fabric.__version_info__)

print("dir(fabric)")
print(dir(fabric))

import getpass
host = "catafest@tty.sdf.org"
password = getpass.getpass('Password for SDF account:')
with Connection("catafest@tty.sdf.org", connect_kwargs={"password":password}) as con:
    print("I will run command: ls")
    con.run("ls")
    
# using the task decorator 
from fabric import task
@task    
def processes(con):
    return con.run("ps -aux", hide = True).stdout.strip()

# print processes
print(processes(con))
con.run("exit")
# use the import for multiple host with all modules

from fabric import Connection, Config, SerialGroup, ThreadingGroup, exceptions, runners
from fabric.exceptions import GroupException

hosts = "catafest@tty.sdf.org,catafest@tty.sdf.org"

def testHosts(hosts):
    # Get list of hosts from somewhere, and convert them to connections
    hosts = hosts.split(",")
    servers = [Connection(host=host,connect_kwargs={"password":password}) for host in hosts]
    thread_group = ThreadingGroup.from_connections(servers)
    results = thread_group.run("who -a", hide=True)
    for r in results:
        connection = results[r]
        return connection.stdout.strip() 
        
print(testHosts(hosts))

The result of this python script:

fabric.__version__
2.5.0
fabric.__version_info__
(2, 5, 0)
dir(fabric)
['Config', 'Connection', 'Executor', 'Group', 'GroupResult', 'Remote', 'Result', 'SerialGroup', 'Task', 
'ThreadingGroup', '__builtins__', '__cached__', '__doc__', '__file__', '__loader__', '__name__', 
'__package__', '__path__', '__spec__', '__version__', '__version_info__', '_version', 'config', 'connection', 
'exceptions', 'executor', 'group', 'runners', 'task', 'tasks', 'transfer', 'tunnels', 'util']
Password for SDF account:
I will run command: ls
USER            PID %CPU %MEM    VSZ    RSS TTY     STAT STARTED     TIME COMMAND
...
catafest      10431  0.0  0.0  30496   3120 ?       S     5:50PM  0:00.00 sshd:
...
catafest      19243  0.0  0.0  12008   1096 ?       O     5:50PM  0:00.00 ps -a
...
user   pts/0    Jun  7 17:40 00:10         0  term=0 exit=0 sess=0 type=user process  ...

Python 3.8.3 : Using the fabric python module - part 001.

The tutorial for today is about fabric python module.

You can read about this python module on the official webpage.

The team comes with this intro:

Fabric is a high level Python (2.7, 3.4+) library designed to execute shell commands remotely over SSH, yielding useful Python objects in return

...

It builds on top of Invoke (subprocess command execution and command-line features) and Paramiko (SSH protocol implementation), extending their APIs to complement one another and provide additional functionality.

I used python version 3.8.3rc1 to install with the pip3 tool.

pip3 install fabric
Collecting fabric
...
Installing collected packages: invoke, fabric
Successfully installed fabric-2.5.0 invoke-1.4.1

from fabric import Connection
import getpass
host = "catafest@tty.sdf.org"
password = getpass.getpass('Password for SDF account:')
with Connection("catafest@tty.sdf.org", connect_kwargs={"password":password}) as con:
    print("I will run command: id -u -n")
    con.run("id -u -n")
    print("I will run command: df -h")
    con.run("df -h")
    print("I will run command for SDF help: help")
    con.run("help")
    out = con.run("free")
    print("output for dir(out)")
    print(dir(out))
    print("output for out.shell")
    print(out.shell)
    print("output for out.connection")
    print(out.connection)
    print("output for out.stdout")
    print(out.stdout)
    print("output for out.env")
    print(out.env)

This is a simple example tested on my SDF account.

About the SDF:

The Super Dimension Fortress is a networked community of free software
authors, teachers, librarians, students, researchers, hobbyists,
computer enthusiasts, the aural and visually impaired. It is operated
as a recognized non-profit 501(c)(7) and is supported by its members.

Our mission is to provide remotely accessible computing facilities for
the advancement of public education, cultural enrichment, scientific
research and recreation. Members can interact electronically with each
other regardless of their location using passive or interactive forums.
Further purposes include the recreational exchange of information
concerning the Liberal and Fine Arts.

Members have UNIX shell access to games, email, usenet, chat, bboard,
webspace, gopherspace, programming utilities, archivers, browsers, and
more. The SDF community is made up of caring, highly skilled people who
operate behind the scenes to maintain a non-commercial INTERNET.

For information about membership levels, click on 'join' above.

Let see my example:

python fabric_001.py
Password for SDF account:
I will run command: id -u -n
catafest
I will run command: df -h
Filesystem         Size       Used      Avail %Cap Mounted on
/dev/wd0a           35G       2.0G        31G   6% /
nol1:/sdf           23T       5.1T        17T  23% /sdf
ptyfs              1.0K       1.0K         0B 100% /dev/pts
I will run command for SDF help: help
tput: No terminal type specified and no TERM variable set in the environment.
SDF Help System - v8, 1993 - sdf!smj

 [a] Directory and File Utilities
 [b] Email Information
 [c] USENET Information
 [d] User and Process Information
 [e] Tutorials and Very Useful Commands
 [f] ARPA Services (internetworking)
 [g] Homepage, VHOST and MetaARPA Utilities

 [q] Quit SDF Help System

Your Choice? q
q
For more help, type 'faq'
For a list of basic UNIX commands, type 'unix'
For live help, type 'helpdesk'

             total       used       free    buffers
Mem:      16274580   15098664    1175916   13433820
Swap:      1049292          0    1049292
output for dir(out)
['__bool__', '__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', 
'__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', 
'__ne__', '__new__', '__nonzero__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', 
'__str__', '__subclasshook__', '__weakref__', 'command', 'connection', 'encoding', 'env', 'exited', 'failed', 
'hide', 'ok', 'pty', 'return_code', 'shell', 'stderr', 'stdout', 'tail']
output for out.shell
C:\Windows\system32\cmd.exe
output for out.connection
<Connection host=tty.sdf.org user=catafest>
output for out.stdout
             total       used       free    buffers
Mem:      16274580   15098664    1175916   13433820
Swap:      1049292          0    1049292

output for out.env
{}

Python Qt5 : PyQt5 and PyGame compatibility with source code.

This tutorial tries to solve from the objectives related to solving and stabilizing compatibility errors between PyQt4 and PyQt5 and creating a common interface between PyQt5 and PyGame.

There is always the same problem in programming when the developer for some reason has to change classes, methods and functions and reusing the old code is no longer valid.

In this case, common or other errors occur, which leads to a waste of time.

I will present a simple way to solve these problems.

I really like to use the PyQt5 module to create interfaces for my python programs and scripts.

Like any programmer who hasn't fully used all A.P.I, I always use the old source code I programmed in the past.

What the developer says about the transition from PyQt4 to PyQt5 we can see on the official page.

Obviously, you will have to move on to things to know but it is quite difficult to always come back and read this content when you have programming errors.

Today, I wanted to make a simple drawing interface in PyGame that would be included in a PyQt5 interface.

I tried to use an old code created by me in PyQt4 but I realized that I had encountered errors before switching to the new PyQt5.

This compatibility problem generates errors and can be solved as follows: by knowing the exact solution and fixing errors in real time, studying the changes created by the developer or the classic search for errors.

My solution comes with the help of these solutions and requires a simple step using the commented source code.

To show you how simple it is to understand I will show you the source code for the interface I built that simply to solves the problem of understanding compatibility by reading the developer source code with simple and useful comments.

#the old import for PyQt4
#from PyQt4 import QtGui

#the new import for PyQt5
#from PyQt5 import QtCore, QtGui, QtWidgets
#class MainWindow(QtWidgets.QMainWindow, UI.MainUI.Ui_MainWindow):

from PyQt5 import QtGui
from PyQt5 import QtWidgets
import pygame
import sys

# old definition for PyQt4 for QWidget
#class ImageWidget(QtGui.QWidget):
class ImageWidget(QtWidgets.QWidget):   
    def __init__(self,surface,parent=None):
        super(ImageWidget,self).__init__(parent)
        w=surface.get_width()
        h=surface.get_height()
        self.data=surface.get_buffer().raw
        self.image=QtGui.QImage(self.data,w,h,QtGui.QImage.Format_RGB32)

    def paintEvent(self,event):
        my_paint=QtGui.QPainter()
        # the definitions for PyQt4 and PyQt5 use QtGui.QPainter()     
        my_paint.begin(self)
        my_paint.drawImage(0,0,self.image)
        my_paint.end()
        
# old definition for PyQt4 for QMainWindow
#class MainWindow(QtGui.QMainWindow):
class MainWindow(QtWidgets.QMainWindow):
    def __init__(self,surface,parent=None):
        super(MainWindow,self).__init__(parent)
        self.setFixedSize(640, 480)
        self.setCentralWidget(ImageWidget(surface))
# this part of source code need to be updated if you want to use animation        
# init PyGame 
pygame.init()
# define a surface 
my_surface=pygame.Surface((640,480))
# fill the surface, see https://www.pygame.org/docs/ref/surface.html#pygame.Surface.fill
my_surface.fill((0,0,255,176))
# draw circle see https://www.pygame.org/docs/ref/draw.html#pygame.draw.circle
pygame.draw.circle(my_surface,(0,0,127,255),(76,76),76)
# draw ellipse (surface, color(R,G,B), size (x,y,x+dx, y+y+dy) )
pygame.draw.ellipse(my_surface,(127,0,0,0),(0,0,12,76))
 
# this part of source code will show 
# the my_surface created with PyGame in PyQt5
# old definition for PyQt4
#app=QtGui.QApplication(sys.argv)
app=QtWidgets.QApplication(sys.argv)
my_window=MainWindow(my_surface)
my_window.show()
app.exec_()

Python 3.8.3 : A brief introduction to the Celery python package.

The development team tells us:

Celery is a simple, flexible, and reliable distributed system to process vast amounts of messages, while providing operations with the tools required to maintain such a system.

To do that Celery uses tasks.

These task queues are used as a mechanism to distribute work across threads or machines using brokers.

A task a client puts a message on the queue and the broker then delivers the message to a worker.

The install of this python package is simple:

Celery can run on a single machine, on multiple machines, or even across datacenters.

pip3 install -U Celery
Collecting Celery
...
Installing collected packages: pytz, billiard, vine, amqp, kombu, Celery
Successfully installed Celery-4.4.2 amqp-2.5.2 billiard-3.6.3.0 kombu-4.6.8 pytz-2020.1 vine-1.3.0

The Celery library must be instantiated before use like an application.

First, I tested with a simple example application from the official website.

from celery import Celery
app = Celery()

@app.task
def add(x, y): return x + y

if __name__ == '__main__':
    app.worker_main()

When I run it this application the output is this:

python.exe .\example_tasks.py
 
 -------------- celery@DESKTOP-9DSLSMF v4.4.2 (cliffs)
--- ***** ----- 
-- ******* ---- Windows-10-10.0.18362-SP0 2020-05-24 18:30:04
- *** --- * --- 
- ** ---------- [config]
- ** ---------- .> app:         __main__:0x1c697187940
- ** ---------- .> transport:   amqp://guest:**@localhost:5672//
- ** ---------- .> results:     disabled://
- *** --- * --- .> concurrency: 6 (prefork)
                .> celery           exchange=celery(direct) key=celery


[2020-05-24 18:30:06,273: ERROR/MainProcess] consumer: Cannot connect to amqp://guest:**@127.0.0.1:5672//:
[WinError 10061] No connection could be made because the target machine actively refused it.
Trying again in 2.00 seconds... (1/100)

[2020-05-24 18:30:10,296: ERROR/MainProcess] consumer: Cannot connect to amqp://guest:**@127.0.0.1:5672//:
[WinError 10061] No connection could be made because the target machine actively refused it.
Trying again in 4.00 seconds... (2/100)

[2020-05-24 18:30:16,323: ERROR/MainProcess] consumer: Cannot connect to amqp://guest:**@127.0.0.1:5672//:
[WinError 10061] No connection could be made because the target machine actively refused it.
Trying again in 6.00 seconds... (3/100)


worker: Hitting Ctrl+C again will terminate all running tasks!

worker: Warm shutdown (MainProcess)

This error is show because I trying to connect to a local instance of default broker named RabbitMQ .

RabbitMQ is most popular open source message broker and can be download it from the official webpage.

If you want to install RabbitMQ, then you need to install Erlang, see screenshot:

This is not the only one option, you have many features like for example Redis.

The development team try experimental support for a myriad of other solutions, including using SQLite for local development.

A full list with all supported brokers can be found here.

Celery is easy to integrate with web frameworks, some of them even have integration packages:

• Pyramid  with pyramid_celery;
• Pylons with celery-pylons;
• Flask not needed;
• web2py with web2py-celery;
• Tornado with tornado-celery;
• Tryton with celery_tryton;
• and Django also no not needed because works well.
  

Maybe I will make another tutorial about this python module and how works with Redis or Django.