Category Archives: Software development

Validate IP Addresses and Networks with CIDR in Python

Python has a built-in package named ipaddress

You don’t need to install anything to use it.

This simple code shows how to use it

import ipaddress


def check_ip(s_ip_or_net):
    b_valid = True
    try:
        # The IP Addresses are expected to be passed without / even if it's /32 it would fail
        # If it uses / so, the CIDR notation, check it as a Network, even if it's /32
        if "/" in s_ip_or_net:
            o_net = ipaddress.ip_network(s_ip_or_net)
        else:
            o_ip = ipaddress.ip_address(s_ip_or_net)

    except ValueError:
        b_valid = False

    return b_valid


if __name__ == "__main__":
    a_ips = ["127.0.0.2.4",
             "127.0.0.0",
             "192.168.0.0",
             "192.168.0.1",
             "192.168.0.1 ",
             "192.168.0. 1",
             "192.168.0.1/32",
             "192.168.0.1 /32",
             "192.168.0.0/32",
             "192.0.2.0/255.255.255.0",
             "0.0.0.0/31",
             "0.0.0.0/32",
             "0.0.0.0/33",
             "1.2.3.4",
             "1.2.3.4/24",
             "1.2.3.0/24"]

    for s_ip in a_ips:
        b_success = check_ip(s_ip)
        if b_success is True:
            print(f"The IP Address or Network {s_ip} is valid")
        else:
            print(f"The IP Address or Network {s_ip} is not valid")

And the output is like this:

The IP Address or Network 127.0.0.2.4 is not valid
The IP Address or Network 127.0.0.0 is valid
The IP Address or Network 192.168.0.0 is valid
The IP Address or Network 192.168.0.1 is valid
The IP Address or Network 192.168.0.1  is not valid
The IP Address or Network 192.168.0. 1 is not valid
The IP Address or Network 192.168.0.1/32 is valid
The IP Address or Network 192.168.0.1 /32 is not valid
The IP Address or Network 192.168.0.0/32 is valid
The IP Address or Network 192.0.2.0/255.255.255.0 is valid
The IP Address or Network 0.0.0.0/31 is valid
The IP Address or Network 0.0.0.0/32 is valid
The IP Address or Network 0.0.0.0/33 is not valid
The IP Address or Network 1.2.3.4 is valid
The IP Address or Network 1.2.3.4/24 is not valid
The IP Address or Network 1.2.3.0/24 is valid

As you can read in the code comments, ipaddress.ip_address() will not validate an IP Address with the CIDR notation, even if it’s /32.

You should strip the /32 or use ipaddress.ip_network() instead.

As you can see 1.2.3.4/24 is returned as not valid.

You can pass the parameter strict=False and it will be returned as valid.

ipaddress.ip_network(s_ip_or_net, strict=False)

Creating a RabbitMQ Docker Container accessed with Python and pika

In this video, that I streamed on Twitch, I demonstrate the code showed here.

I launch the Docker Container and operated it a bit, so you can get to learn few tricks.

I created the RabbitMQ Docker installation based on the official RabbitMQ installation instructions for Ubuntu/Debian:

https://www.rabbitmq.com/install-debian.html#apt-cloudsmith

One interesting aspect is that I cover how the messages are delivered as byte sequence. I show this by sending Unicode characters

Files in the project

Dockerfile

FROM ubuntu:20.04

MAINTAINER Carles Mateo

ARG DEBIAN_FRONTEND=noninteractive

# This will make sure printing in the Screen when running in dettached mode
ENV PYTHONUNBUFFERED=1

ARG PATH_RABBIT_INSTALL=/tmp/rabbit_install/

ARG PATH_RABBIT_APP_PYTHON=/opt/rabbit_python/

RUN mkdir $PATH_RABBIT_INSTALL

COPY cloudsmith.sh $PATH_RABBIT_INSTALL

RUN chmod +x ${PATH_RABBIT_INSTALL}cloudsmith.sh

RUN apt-get update -y && apt install -y sudo python3 python3-pip mc htop less strace zip gzip lynx && apt-get clean

RUN ${PATH_RABBIT_INSTALL}cloudsmith.sh

RUN service rabbitmq-server start

RUN mkdir $PATH_RABBIT_APP_PYTHON

COPY requirements.txt $PATH_RABBIT_APP_PYTHON

WORKDIR $PATH_RABBIT_APP_PYTHON

RUN pwd

RUN pip install -r requirements.txt

COPY *.py $PATH_RABBIT_APP_PYTHON

COPY loop_send_get_messages.sh $PATH_RABBIT_APP_PYTHON

RUN chmod +x loop_send_get_messages.sh

CMD ./loop_send_get_messages.sh

cloudsmith.sh

#!/usr/bin/sh
# From: https://www.rabbitmq.com/install-debian.html#apt-cloudsmith

sudo apt-get update -y && apt-get install curl gnupg apt-transport-https -y

## Team RabbitMQ's main signing key
curl -1sLf "https://keys.openpgp.org/vks/v1/by-fingerprint/0A9AF2115F4687BD29803A206B73A36E6026DFCA" | sudo gpg --dearmor | sudo tee /usr/share/keyrings/com.rabbitmq.team.gpg > /dev/null
## Cloudsmith: modern Erlang repository
curl -1sLf https://dl.cloudsmith.io/public/rabbitmq/rabbitmq-erlang/gpg.E495BB49CC4BBE5B.key | sudo gpg --dearmor | sudo tee /usr/share/keyrings/io.cloudsmith.rabbitmq.E495BB49CC4BBE5B.gpg > /dev/null
## Cloudsmith: RabbitMQ repository
curl -1sLf https://dl.cloudsmith.io/public/rabbitmq/rabbitmq-server/gpg.9F4587F226208342.key | sudo gpg --dearmor | sudo tee /usr/share/keyrings/io.cloudsmith.rabbitmq.9F4587F226208342.gpg > /dev/null

## Add apt repositories maintained by Team RabbitMQ
sudo tee /etc/apt/sources.list.d/rabbitmq.list <<EOF
## Provides modern Erlang/OTP releases
##
deb [signed-by=/usr/share/keyrings/io.cloudsmith.rabbitmq.E495BB49CC4BBE5B.gpg] https://dl.cloudsmith.io/public/rabbitmq/rabbitmq-erlang/deb/ubuntu bionic main
deb-src [signed-by=/usr/share/keyrings/io.cloudsmith.rabbitmq.E495BB49CC4BBE5B.gpg] https://dl.cloudsmith.io/public/rabbitmq/rabbitmq-erlang/deb/ubuntu bionic main

## Provides RabbitMQ
##
deb [signed-by=/usr/share/keyrings/io.cloudsmith.rabbitmq.9F4587F226208342.gpg] https://dl.cloudsmith.io/public/rabbitmq/rabbitmq-server/deb/ubuntu bionic main
deb-src [signed-by=/usr/share/keyrings/io.cloudsmith.rabbitmq.9F4587F226208342.gpg] https://dl.cloudsmith.io/public/rabbitmq/rabbitmq-server/deb/ubuntu bionic main
EOF

## Update package indices
sudo apt-get update -y

## Install Erlang packages
sudo apt-get install -y erlang-base \
                        erlang-asn1 erlang-crypto erlang-eldap erlang-ftp erlang-inets \
                        erlang-mnesia erlang-os-mon erlang-parsetools erlang-public-key \
                        erlang-runtime-tools erlang-snmp erlang-ssl \
                        erlang-syntax-tools erlang-tftp erlang-tools erlang-xmerl

## Install rabbitmq-server and its dependencies
sudo apt-get install rabbitmq-server -y --fix-missing

build_docker.sh

#!/bin/bash

s_DOCKER_IMAGE_NAME="rabbitmq"

echo "We will build the Docker Image and name it: ${s_DOCKER_IMAGE_NAME}"
echo "After, we will be able to run a Docker Container based on it."

printf "Removing old image %s\n" "${s_DOCKER_IMAGE_NAME}"
sudo docker rm "${s_DOCKER_IMAGE_NAME}"

printf "Creating Docker Image %s\n" "${s_DOCKER_IMAGE_NAME}"
sudo docker build -t ${s_DOCKER_IMAGE_NAME} . --no-cache

i_EXIT_CODE=$?
if [ $i_EXIT_CODE -ne 0 ]; then
    printf "Error. Exit code %s\n" ${i_EXIT_CODE}
    exit
fi

echo "Ready to run ${s_DOCKER_IMAGE_NAME} Docker Container"
echo "To run in type: sudo docker run -it --name ${s_DOCKER_IMAGE_NAME} ${s_DOCKER_IMAGE_NAME}"
echo "or just use run_in_docker.sh"

requirements.txt

pika

loop_send_get_messages.sh

#!/bin/bash

echo "Starting RabbitMQ"
service rabbitmq-server start

echo "Launching consumer in background which will be listening and executing the callback function"
python3 rabbitmq_getfrom.py &

while true; do

    i_MESSAGES=$(( RANDOM % 10 ))

    echo "Sending $i_MESSAGES messages"
    for i_MESSAGE in $(seq 1 $i_MESSAGES); do
        python3 rabbitmq_sendto.py
    done

    echo "Sleeping 5 seconds"
    sleep 5

done

echo "Exiting loop"

rabbitmq_sendto.py

#!/usr/bin/env python3
import pika
import time

connection = pika.BlockingConnection(pika.ConnectionParameters(host="localhost"))

channel = connection.channel()

channel.queue_declare(queue="hello")

s_now = str(time.time())

s_message = "Hello World! " + s_now + " Testing Unicode: çÇ àá😀"
channel.basic_publish(exchange="", routing_key="hello", body=s_message)
print(" [x] Sent '" + s_message + "'")
connection.close()

rabbitmq_getfrom.py

#!/usr/bin/env python3
import pika


def callback(ch, method, properties, body):
    # print(f" [x] Received in channel: {ch} method: {method} properties: {properties} body: {body}")
    print(f" [x] Received body: {body}")


connection = pika.BlockingConnection(pika.ConnectionParameters(host="localhost"))

channel = connection.channel()

channel.queue_declare(queue="hello")

print(" [*] Waiting for messages. To exit press Ctrl+C")

# This will loop
channel.basic_consume(queue="hello", on_message_callback=callback)
channel.start_consuming()

print("Finishing consumer")

Video: Parse the Tables from a Website with Python pandas

A quick video, of 3 minutes, that shows you how it works.

If you don’t have pandas installed you’ll have to install it and lxml, otherwise you’ll get an error:

  File "/home/carles/Desktop/code/carles/blog.carlesmateo.com-source-code/venv/lib/python3.8/site-packages/pandas/io/html.py", line 872, in _parser_dispatch
    raise ImportError("lxml not found, please install it")
ImportError: lxml not found, please install it

You can install both from PyCharm or from command line with:

pip install pandas
pip install lxml

And here the source code:

import pandas as pd


if __name__ == "__main__":

    # Do not truncate the data when printing
    pd.set_option('display.max_colwidth', None)
    # Do not truncate due to length of all the columns
    pd.set_option('display.max_columns', None)
    pd.set_option('display.max_rows', None)
    pd.set_option('display.width', 2000)
    # pd.set_option('display.float_format', '{:20,.2f}'.format)

    o_pd_my_movies = pd.read_html("https://blog.carlesmateo.com/movies-i-saw/")
    print(len(o_pd_my_movies))

    print(o_pd_my_movies[0])

Video: How to create a Docker Container for LAMPP step by step

How to create a Docker Container for Linux Apache MySQL PHP and Python for beginners.

Note: Containers are not persistent. Use this for tests only. If you want to keep persistent information use Volumes.

Sources: https://gitlab.com/carles.mateo/blog.carlesmateo.com-source-code/-/tree/master/twitch/live_20220708_dockerfile_lamp

File: Dockerfile

FROM ubuntu:20.04

MAINTAINER Carles Mateo

ARG DEBIAN_FRONTEND=noninteractive

RUN apt update && \
    apt install -y vim python3-pip &&  \
    apt install -y net-tools mc vim htop less strace zip gzip lynx && \
    apt install -y apache2 mysql-server ntpdate libapache2-mod-php7.4 mysql-server php7.4-mysql php-dev libmcrypt-dev php-pear && \
    apt install -y git && apt autoremove && apt clean && \
    pip3 install pytest

RUN a2enmod rewrite

RUN echo "Europe/Ireland" | tee /etc/timezone

ENV APACHE_RUN_USER  www-data
ENV APACHE_RUN_GROUP www-data
ENV APACHE_LOG_DIR   /var/log/apache2
ENV APACHE_PID_FILE  /var/run/apache2/apache2.pid
ENV APACHE_RUN_DIR   /var/run/apache2
ENV APACHE_LOCK_DIR  /var/lock/apache2
ENV APACHE_LOG_DIR   /var/log/apache2

COPY phpinfo.php /var/www/html/

RUN service apache2 restart

EXPOSE 80

CMD ["/usr/sbin/apache2", "-D", "FOREGROUND"]

File: phpinfo.php

<html>
<?php

// Show all information, defaults to INFO_ALL
phpinfo();

// Show just the module information.
// phpinfo(8) yields identical results.
phpinfo(INFO_MODULES);
?>
</html>

File: build_docker.sh

#!/bin/bash

s_DOCKER_IMAGE_NAME="lampp"

echo "We will build the Docker Image and name it: ${s_DOCKER_IMAGE_NAME}"
echo "After, we will be able to run a Docker Container based on it."

printf "Removing old image %s\n" "${s_DOCKER_IMAGE_NAME}"
sudo docker rm "${s_DOCKER_IMAGE_NAME}"

printf "Creating Docker Image %s\n" "${s_DOCKER_IMAGE_NAME}"
# sudo docker build -t ${s_DOCKER_IMAGE_NAME} . --no-cache
sudo docker build -t ${s_DOCKER_IMAGE_NAME} .

i_EXIT_CODE=$?
if [ $i_EXIT_CODE -ne 0 ]; then
    printf "Error. Exit code %s\n" ${i_EXIT_CODE}
    exit
fi

echo "Ready to run ${s_DOCKER_IMAGE_NAME} Docker Container"
echo "To run in type: sudo docker run -p 80:80 --name ${s_DOCKER_IMAGE_NAME} ${s_DOCKER_IMAGE_NAME}"
echo "or just use run_in_docker.sh"

echo
echo "If you want to debug do:"
echo "docker exec -i -t ${s_DOCKER_IMAGE_NAME} /bin/bash"

Solving Linux Load key “ssh_yourserver”: invalid format when provisioning from Jenkins

If you are getting an error like this when you try to provision using rsync or running commands from SSH from a Docker Instance from a worker node in Jenkins, having your SSH Key as a variable in Jenkins, here is a way to solve it.

These are the kind of errors that you’ll be receiving:

Load key "ssh_yourserver": invalid format

web@myserver.carlesmateo.com: Permission denied (publickey).

rsync: connection unexpectedly closed (0 bytes received so far) [sender]

rsync error: unexplained error (code 255) at io.c(235) [sender=3.1.3]

script returned exit code 255

So this applies if you copied your .pem file as text and pasted in a variable in Jenkins.

You’ll find yourself with the load key invalid format error.

I would suggest to use tokens and Vault or Consul instead of pasting a SSH Key, but if you need to just solve this ASAP that’s the trick that you need.

First encode your key with base64 without any wrapping. This is done with this command:

cat keys/key_azure_myserver_carlesmateo_com.pem | base64 --wrap=0

In your Jenkins steps you’ll add this code:

#!/bin/bash
echo "Creating credentials"
echo $SSH_YOURSERVER | base64 --decode > ssh_yourserver
echo "Setting permissions"
chmod 600 ssh_yourserver

Having a certificate then you can define new steps that will deploy to Production by rsyncing:

#!/bin/bash
echo "Deploying www..."
rsync -e "ssh -i ssh_carlesmateo -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null" -av --progress --exclude={} --stats --human-readable -z www/ web@myserver.carlesmateo.com:/var/www/myawesomeproject/www/

Note that in this case I’m ignoring Strict Host Key Checking, which is not the preferred option for security, but you may want to use it depending on your strategy and characteristics of your Cloud Deployments.

Note also that I’m indicating as User Known Hosts File /dev/null. That is something you may want to have is you provision using Docker Containers that immediately destroyed after and Jenkins has not created the user properly and it is unable to write to ~home/.ssh/known_hosts

I mention the typical errors where engineers go crazy and spend more time fixing.

News from the Blog 2022-06-22

For the first part of June I’ve been quiet on Social Media as I was on holidays and taking some scheduled tests for my health in the hospital.

Carles in the Media/Press/Streaming

Twitch

I started streaming live Python coding sessions in Twitch. I’m giving it a try to see if coders have engagement.

The Software I use to broadcast from Linux is OBS.

I started with my Open Source project ctop.

I had a very long and interesting session on 2022-06-06 about OpenZFS, Data Centers, NVMe, iSCSI, Hard Drives, Storage, performance, Data Centers

More funny things happened like when I was installing a VirtualBox VM live, and the ZFS pool became irresponsible due hardware errors in one SATA Spinning drive.

Things from broadcasting live…

Some of the feedback I got from talented Engineers is that even if the original matter to talk about was interesting, seeing everything falling apart live due to unexpected hardware problems, and me troubleshooting live is being the best of the show… which I found very amusing.

RAB Radio the new digital world

I keep doing my radio space for Radio America Barcelona, once per week, addressed to the Catalan Community across the world and expats.

This radio program, streamed also via Twitch, is available in Catalan language only. RAB.

Open Source

carleslibs

I’ve been working in version 1.0.8 branch, and after a session of refactor on Twitch where I found a bug in MenuUtils class, I fixed it and released v. 1.0.8. You can see the video on the link.

Now I’m working on the branch v. 1.0.9.

ctop

I’ve been working in the branch 0.8.9.

My first Twitch broadcast was about adding Unit Testing to MemUtils class.

You can see all my videos:

http://www.youtube.com/channel/UCYzY-2wJ9W_ooR64-QzEdJg

Infrastructure

OpenStack

I recommend you the videos in this page about Operating OpenStack at Scale.

Some of my Blizzard colleagues talk on it.

https://superuser.openstack.org/articles/upgrades-in-large-scale-openstack-infrastructure-openinfra-live-episode-6/

https://www.openstack.org/videos/summits/denver-2019/how-blizzard-entertainment-uses-autoscaling-with-overwatch

My last physical server in a Data Center

This week I decommissioned my last physical server in a Data Center.

It has been a long journey since I created my company to launch my own projects, and I started having my own infrastructure, back at 2000.

I was offering VPS at that time, with VMWare as Hypervisor.

This last Rack Server served me well for 21 years.

Now everything is Cloud, and is not viable to host and maintain servers unless this is your main occupation. Server’s motherboards die, hard drives die and they need to be replaced. Maintaining infrastructure it’s a full time job and you require somebody to do it. Also using fixed servers only prevents you from moving fast, locks a lot of money, and from spawning more compute capacity.

If you are curious this Rack Server is a Super Micro with Intel Xeon processor and SCSI drives.

Security

Firewall

I keep blocking thousands of IP Addresses every day.

When I see a pattern of an IP trying an attacks against the Server I look at the IP and if it’s from a hosting provider I just block the entire range.

I keep blocking any IP Address coming from Russia or Belarus since they invaded Ukraine.

My Health

I visited the hospital for a programmed following on my health.

The analysis are super good, and it’s super clear that I’ve improved radically. My discipline with the diet, taking the medicines and doing exercise regularly has been crucial.

My Doctor is confident that I’ll have a full recovery, but to do so I need to loss a lot of weight in a year or two.

So, I need to focus on my health and in doing exercise, being happy and avoid any kind of negative stress.

The cost of the travels and the medicines have put some stress into my economy, but I’m fortunate that I can handle it.

Entertainment / Life / Reflections

Star Wars and racism

I’m really enjoying new Start Wars series Obi Wan, and I’ve been profoundly shocked to read that there are fans being racist against the black characters.

https://www.theverge.com/2022/5/31/23148468/star-wars-obi-wan-moses-ingram-third-sister

So just writing here to show my support to human beings from all races, genders including transgender, LGTB+, conditions and preferences.

Sorting an Array of Tuples in Python

In this video I show a nice way to work with Data in Python, by using Tuples.

I also show how to easily and conveniently sort the Data based on your preferred criteria by using lambdas.

What happens if we have accents, ç, Ç etc…

You can download the code from:

https://gitlab.com/carles.mateo/python_combat_guide/-/blob/master/src/arrays_with_tuples.py

Fixing the problems installing napalm-base in Ubuntu 20.04 LTS

One of my friends wanted to use SaltStack and https://github.com/napalm-automation/napalm-salt

But he had problems installing napalm-base package.

Note that the package is no longer maintained.

He tried with the last one, and with the previous one (0.25.0), but he always got the error: ModuleNotFoundError: No module named ‘pip.req’

pip3 install napalm-base==0.25.0

Defaulting to user installation because normal site-packages is not writeable
Collecting napalm-base==0.25.0
  Using cached napalm-base-0.25.0.tar.gz (35 kB)
  Preparing metadata (setup.py) ... error
  error: subprocess-exited-with-error
  
  × python setup.py egg_info did not run successfully.
  │ exit code: 1
  ╰─> [6 lines of output]
      Traceback (most recent call last):
        File "<string>", line 2, in <module>
        File "<pip-setuptools-caller>", line 34, in <module>
        File "/tmp/pip-install-gzd07xzq/napalm-base_aace1b03ac0e4045bbc85e27c788ebc1/setup.py", line 5, in <module>
          from pip.req import parse_requirements
      ModuleNotFoundError: No module named 'pip.req'
      [end of output]
  
  note: This error originates from a subprocess, and is likely not a problem with pip.
error: metadata-generation-failed

× Encountered error while generating package metadata.
╰─> See above for output.

note: This is an issue with the package mentioned above, not pip.
hint: See above for details.

TL;TR: The problem is that pip version 10, changed the structure for req.

There are several solutions that can be done to make it work, but the easiest way is to downgrade pip, and install the package. After pip can be upgraded again.

python -m pip install pip==9.0.3
pip3 install napalm-base

Why I think in Python is not a good idea to raise exceptions inside your methods

Last update: 2022-05-18 10:48 Irish Time

Recently a colleague was asking me for advice on their design of error handling in a Python application.

They were catching an error and raising an Exception, inside the except part of a method, to be catch outside the method.

And at some point a simple logic got really messy and unnecessarily complicated. Also troubleshooting and debugging an error was painful because they were only getting a Custom Exception and not context.

I explained to my colleague that I believed that the person that created that Exception chain of catch came from Java background and why I think they choose that path, and why I think in Python it’s a bad idea.

In Java, functions and methods can only return one object.

I programmed a lot in Java in my career, and it was a pain having to create value objects, and having to create all kind of objects for the return. Is it a good thing that types are strongly verified by the language? Yes. It worked? Yes. It made me invest much more time than necessary? Also yes.

Having the possibility to return only one object makes it mandatory having a way to return when there was an error. Otherwise you would need to encapsulate an error code and error description fields in each object, which is contrary to the nature of the object.

For example, a class Persona. Doesn’t make any sense having an attribute inside the class Persona to register if an operation related to this object went wrong.

For example, if we are in a class Spaceship that has a method GetPersonaInCommand() and there is a problem in that method, doesn’t make any sense to return an empty Persona object with attributes idError, errorDescription. Probably the Constructor or Persona will require at least a name or Id to build the object…. so in this case, makes sense that the method raises an Exception so the calling code catches it and knows that something went wrong or when there is no data to return.

This will force to write Custom Exceptions, but it’s a solution.

Another solution is creating a generic response object which could be an Object with these attributes:

  • idError
  • errorDescription
  • an Object which is the response, in our example Persona or null

I created this kind of approach for my Cassandra libraries to easily work with Cassandra from Java and from PHP, and for Cassandra Universal Driver (a http/s gateway created in year 2014).

Why this in not necessary in Python

Python allows you to return multiple values, so I encourage you tor return a boolean for indicating the success of the operation, and the object/value you’re interested.

You can see it easily if you take a look to FileUtils class from my OpenSource libraries carleslibs.

The method get_file_size_in_bytes(self, s_file) for example:

    def get_file_size_in_bytes(self, s_file):

        b_success = False
        i_file_size = 0

        try:
            # This will help with Unit Testing by raisin IOError Exception
            self.test_helper()

            i_file_size = os.path.getsize(s_file)
            b_success = True
        except IOError:
            b_success = False

        return b_success, i_file_size

It will always return a boolean value to indicate success or failure of the operation and an integer for the size of the file.

The calling code will do something like this:

o_fileutils = FileUtils()
b_success, i_bytes = o_fileutils.get_file_size_in_bytes("profile.png")
if b_succes is False:
    print("Error! The file does not exist or cannot be accessed!")
    exit(1)

if i_bytes < 1024:
    print("The profile picture should be at least 1KB")
    exit(1)

print("Profile picture exists and is", i_bytes, " bytes in length!")

The fact that Python can return multiple variables makes super easy dealing with error handling without having to take the road of Custom Exceptions.

And it is Ok if you want to follow this path, but in my opinion, for most of the developers up to Senior levels, it only over complicates the logic of your code and the amount of try/excepts you have to have everywhere.

If you use PHP you can mix different types in an Array, so you can always return an Array with a boolean, or an i_id_error, and your object or data of whatever type it’s.

Getting back to my carleslibs Open Source package, it is super easy to Unit Test these methods.

In my opinion, this level of simplicity, brings only advantages. Including Software Development speed, which is good for the business.

I’m not advocating for not using Custom Exceptions or to not develop a Exceptions Raising strategy if you need it and you know what you’re doing. I’m just suggesting why I think most of the developments in Python do not really need this and only over complicates the development. There are situations where raising exceptions will be a perfectly useful or even the best approach, there are many scenarios, but I think that in most of cases, using raise inside except will only multiply the time of the development and slow down the speed of bringing new features to the business, over complicating Unit Test as well, and be a real pain for the Junior and Intermediate developers.

The Constructor

Obviously, as the Constructor doesn’t return any value, it is perfectly fine to raise an exception in there, or just to use try/except in the code that is instancing the objects.