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Note that the package is no longer maintained.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
Using cached napalm-base-0.25.0.tar.gz (35 kB)
Preparing metadata (setup.py) ... 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.
× 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.
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:
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
# This will help with Unit Testing by raisin IOError Exception
i_file_size = os.path.getsize(s_file)
b_success = True
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!")
if i_bytes < 1024:
print("The profile picture should be at least 1KB")
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.
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.
This is a document previous to a live code review session.
It has the information to prepare for the upcoming code review session, where I plan to share the lessons learned, decision I took, mistakes I did, refactors I had to overcome, and tentatively we will refactor code in order to add some Unit Testing.
I used to play sudoku with my family, so from time to time I do by myself.
Once I found a sudoku that was impossible and it happened that it was a typo from the newspaper, so, when I found another impossible sudoku I wanted to know if it was me, or if there was a typo or similar, so I decided to write a Sudoku Solver that will solve the sudoku for me.
So, I was working on a project and i wanted to test how long a file can be.
The resources I checked, and also the Kernel and C source I reviewed, were pointing that effectively the limit is 255 characters.
But I had one doubt… given that Python 3 String are UTF-8, and that Linux encode by default is UTF-8, will I be able to use 255 characters length, or this will be reduced as the Strings will be encoded as UTF-8 or Unicode?.
So I did a small Proof of Concept.
For the filenames I grabbed a fragment of the translation to English of the book epic book “Tirant lo Blanc” (The White Knight), one of the first books written in Catalan language and the first chivalry novel known in the world. You can download it for free it in:
from carleslibs.fileutils import FileUtils
from colorama import Fore, Back, Style , init
# For Colorama on Windows
def print_error(self, s_text, s_end="\n"):
Prints errors in Red.
print(Fore.RED + s_text)
def print_success(self, s_text, s_end="\n"):
Prints errors in Green.
print(Fore.GREEN + s_text)
def print_label(self, s_text, s_end="\n"):
Prints a label and not the end line
print(Fore.BLUE + s_text, end="")
def return_text_blue(self, s_text):
Restuns a Text
s_text_return = Fore.BLUE + s_text + Style.RESET_ALL
if __name__ == "__main__":
o_color = ColorUtils()
o_file = FileUtils()
s_text = "In the fertile, rich and lovely island of England there lived a most valiant knight, noble by his lineage and much more for his "
s_text += "courage. In his great wisdom and ingenuity he had served the profession of chivalry for many years and with a great deal of honor, "
s_text += "and his fame was widely known throughout the world. His name was Count William of Warwick. This was a very strong knight "
s_text += "who, in his virile youth, had practiced the use of arms, following wars on sea as well as land, and he had brought many "
s_text += "battles to a successful conclusion."
o_color.print_label("Erasure Code project by Carles Mateo")
print("Task 237 - Proof of Concep of Long File Names, encoded is ASCii, in Linux ext3 and ext4 Filesystems")
print("Using as a sample a text based on the translation of Tirant Lo Blanc")
print("Sample text used:")
print("-" * 30)
print("This test uses the OpenSource libraries from Carles Mateo carleslibs")
s_dir = "task237_tests"
if o_file.folder_exists(s_dir) is True:
o_color.print_success("Directory " + s_dir + " already existed, skipping creation")
b_success = o_file.create_folder(s_dir)
if b_success is True:
o_color.print_success("Directory " + s_dir + " created successfully")
o_color.print_error("Directory " + s_dir + " creation failed")
for i_length in range(200, 512, 1):
s_filename = s_dir + "/" + s_text[0:i_length]
b_success = o_file.write(s_file=s_filename, s_text=s_text)
s_output = "Writing file length: "
print(" file name: ", end="")
print(": ", end="")
if b_success is False:
# Note: up to 255 work, 256 fails
I tried this in an Ubuntu Virtual Box VM.
As part of my tests I tried to add a non typical character in English, ASCii >127, like Ç.
When I use ASCii character < 128 (0 to 127) for the filenames in ext3/ext4 and in a ZFS Pool, I can use 255 positions. But when I add characters that are not typical, like the Catalan ç Ç or accents Àí the space available is reduced, suggesting the characters are being encoded:
Ç has value 128 in the ASCii table and ç 135.
I used my Open Source carleslibs and the package colorama.
I’m Catalan. In 1936 the fascist military leaded by franco raised in arms against the elected government of the Spanish Republic. The Italian and nazi German fascist in power bombed the Catalan population. Hundreds of thousands of innocent citizens were assassinated and millions of Catalan and Spaniards had to exile. The sons of those that were ruling with the dictator have been insisting in naming it a “civil war”, but it was the military lead by a fascist, revolting against the legitimate Republic and ending a democracy.
The dictatorship lasted until 1975, when the dictator died in the bed. The effects of the repression never abandoned Catalonia, and nowadays in Catalonia people is still detained by the Spanish police for talking the Catalan language in front of them, and our Parliament decisions are cancelled by the Spanish courts, for example to force the exit of a President of Catalonia that they didn’t like, or to force the Catalan schools to teach 25% of the time in Spanish attacking the Catalan teaching system.
During WW2 millions of Jews were mass murdered, also people from all the nations were assassinated.
Russian population suffered a lot also fighting the nazis.
Now we have to see how Russia’s army is invading Ukraine and murdering innocent citizens.
I know Engineers from Ukraine. Those guys were doing great building wealthy based on knowledge and working well for companies across the world. Now these people are being killed or Engineers, amongst all the brave population, are arming themselves to fight the invasion. Shells destroy beautiful cities and population are starving, and young soldiers from both sides will never be seen again by their mothers.
Let music play in solidarity with Ukraine. First is a Catalan group. Second is a famous Irish band in this epic song dedicated to the brave International Brigades, volunteers that fought the fascism in Spain and in Catalonia trying to make a better world.
I’ve updated the SSL Certificate. The previous one I bought was issued for two years, and I renewed as it was due to expire.
Honestly, my ego was flattered. It is a lot of reputation.
Although in the past I got an offer from another monstrously big editorial to publish world wide my book Python 3 Combat Guide and I also rejected, and an offer from a digital learning platform to create an interactive course from this same book.
I’ve rejected it again this time.
If you are curious, this is what I answered to them:
I'm well, thank you. I hope you are doing well too.
Thanks for taking the time to explain your conditions to me.
I feel flattered by your editorial thinking about me. I respect your brand, as I mentioned, as I own several of your titles.
However, I have to refuse your offer.
Is not the first time an editor has offered to publish one or more of my books. For all over the world, with much higher economic expectations.
I'll tell you why I love being at LeanPub:
1- I own the rights. All of them.
2- I can publish updates, and my readers get them for free. As I add new materials, the value is maximized for my readers.
3- I get 80% of the royalties.
4- If a reader is not happy, they can return the book for 60 days.
5- I can create vouchers and give a discount to certain readers, or give for free to people that are poor and are trying to get a career in Engineering.
The community of readers are very honest, and I only got 2 returns. One of them I think was from an editorial that purchased the book, evaluated it, and they contacted me to publish it, and after I rejected they applied for the refund.
I teach classes, and I charge 125 EUR per hour. I can make much more by my side than the one time payment you offer. The compensation for the video seems really obsolete.
Also, I could be using Amazon self publishing, which also brings bigger margins than you.
So many thanks for your offer. I thought about it because of the reputation, but I already have a reputation. I've thousands of visits to my tech blog, and because of the higher royalties, even if I sell less books through LeanPub it is much more rewarding.
Thanks again and have a lovely day and rest of the week.
The provisioning in Amazon AWS through their SDK is a book I’m particularly proud, as it empowers the developers so much. And I provide source code so they can go from zero to hero, in a moment. Amazon should provide a project sample as I do, not difficult to follow documentation.
Teaching / Mentoring
As I was requested, I’ve been offering advice and having virtual coffees with some people that recently started their journey to become Software Engineers and wanted some guidance and advice.
It has been great seeing people putting passion and studying hard to make a better future for themselves and for their families.
I’ll probably add to the blog more contents for beginners, although it will continue being a blog dedicated to extreme IT, and to super cool Engineering skills and troubleshooting.
For my regular students I have a discord space where we can talk and they can meet new friends studying or working in Engineering.
This github link provides many free books in multiple languages:
Zoom can zoom the view. So if they are sharing their screen, and font is too small, you can give a relax to your eyes by using Zoom’s zoom feature. It is located in View.
After being in the hospital in December 2021, with risk for my life, and after my incredible recuperation, I’ve got the good news that I don’t need anymore 2 of the 3 medicines I was taking in a daily basis. It looks well through a completely recovery thanks to my discipline, doing sport every day several times, and the fantastic Catalan doctors that are supporting me so well.
Since they found what was failing in me, and after the emergency treatments I started to sleep really well. All night. That’s a privilege that I didn’t have for long long time.
The Unix Epoch is the time, in seconds, that has passed since 1970-01-01 00:00:00 UTC.
# Date time methods
# Author: Carles Mateo
# Creation Date: 2019-11-20 17:23 IST
# Description: Class to return Date, datetime, Unix EPOCH timestamp
Will return the EPOCH Time. For convenience is returned as String
s_now_epoch = str(int(time.time()))
def get_datetime(self, b_milliseconds=False):
Return the datetime with miliseconds in format YYYY-MM-DD HH:MM:SS.xxxxx
or without milliseconds as YYYY-MM-DD HH:MM:SS"""
if b_milliseconds is True:
s_now = str(datetime.datetime.now())
s_now = str(datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S"))
o_datetime = DateTimeUtils()
s_now_epoch = o_datetime.get_unix_epoch()
s_now_date = o_datetime.get_datetime()
The change of license of Docker Desktop for Windows has been a low punch, a dirty one.
Many big companies use Windows as for the laptops and workstations, we like it or not.
You can setup a Linux development computer or Virtual Machine, you may argue, but things are not as easier.
Big companies have Software licenses assigned to corporation machines, so you may not use your Pycharm license in a Linux VM.
You may no use Docker Desktop either, if your company did not license it.
And finally you may need to have access to internal resources, like Artifactory, or Servers where access is granted via ACL, so only you, from your Development machine can access it. So you have to be able to run Docker locally.
After Docker introduced this changed of license I was using VirtualBox with NAT attached to the VPN Virtual Ethernet, and I port forwarded to be able to SSH, deploy, test, etc… from outside to my Linux VM, and it was working for a while, until with the last VirtualBox update and some Windows updates where pushed to my Windows box and my VirtualBox VMs stopped booting most of the times and having random problems.
I configured a new Linux VM in a Development Server, and I opened Docker API so my Pycharm’s workstation was able to deploy there and I was able to test. But the Dev Ip’s do not have access to the same Test Servers I need my Python Automation projects to reach (and quickly I used 50 GB of space), so I tried WSL. I like Pycharm I didn’t want to switch to VStudio Code because of their good Docker extensions, in any case I could not run my code locally with venv cause some of the packages where not available for Windows, so I needed Linux to run the Unit Testing and see the Code Coverage, run the code, etc…
I tried Hyper-V, tried with NAT External, but it was incompatible with my VPN.
Note: WSL can be used, but I wanted to use Docker Engine, not docker in WSL.
Installing Docker Command line binaries
The first thing I checked was the Docker downloads page.
from urllib import request
from bs4 import BeautifulSoup
s_url = "https://blog.carlesmateo.com/movies-i-saw/"
s_html = request.urlopen(s_url).read().decode('utf8')
o_soup = BeautifulSoup(s_html, 'html.parser')
o_title = o_soup.find('title')
print(o_title.string) # Prints the tag string content
# Another possible way
if o_soup.title is not None:
s_title = o_soup.title.string
s_title = o_title.title
sudo apt install python2 python3 python3-pip
# Install boto for Python 2 for Ansible (alternative way if pip install boto doesn't work for you)
python2 -m pip install boto
# Install Ansible
sudo apt install ansible
If you want to use Dynamic Inventory
So you can use the Python 2 ec2.py and ec2.ini files, adding them as to the /etc/ansible with mask +x, to use the Dynamic Inventory.
Then use the calls inside the shell script, or assuming that the previous file was named credentiasl.sh use source credentials.sh
ec2.py is written in Python 2, so probably will fail for you as it is invoked by python and your default interpreter will be Python 3.
So edit the first line of /etc/ansible/ec2.py and add:
Once credentials.sh is sourced, then you can just invoke ec2.py to get the list of your Instances in a JSON format dumped by ec2.py
You can get that JSON file and load it and get the information you need, filtering by group.
You can call:
/etc/ansible/ec2.py --list > instances.json
Or you can run a Python program that escapes to shell and executes ec2.py –list and loads the Output as a JSON file.
I use my carleslibs here to escape to shell using my class SubProcessUtils. You can install them, they are Open Source, or you can code manually if you prefer importing subprocess Python library and catching the stdout, stderr.
from carleslibs import SubProcessUtils
if __name__ == "__main__":
s_command = "/etc/ansible/ec2.py"
o_subprocess = SubProcessUtils()
i_error_code, s_output, s_error = o_subprocess.execute_command_for_output(s_command, b_shell=True, b_convert_to_ascii=True, b_convert_to_utf8=False)
if i_error_code != 0:
print("Error escaping to shell!", i_error_code)
json = json.loads(s_output)
d_hosts = json["_meta"]["hostvars"]
for s_host in d_hosts:
# You'll get a ip/hostnamename in s_host which is the key
# You have to check for groups and the value for the key Name, in order to get the Name of the group
# As an exercise, print(d_hosts[s_host]) and look for:
# @TODO: Capture the s_group_name
# @TODO: Capture the s_addres
if s_group_name == "yourgroup":
# This filters only the instances with your group name, as you want to create an inventory file just for them
# That's because you don't want to launch the playbook for all the instances, but for those in your group name in the inventory file.
# After this you can parse you list a_hostnames and generate an inventory file yourinventoryfile
# The [ec2hosts] in your inventory file must match the hosts section in your yaml files
# You'll execute your playbook with:
# ansible-playbook -i yourinventoryfile youryamlfile.yaml
So an example of a yaml to install Apache2 in Ubuntu 20.04 LTS spawned instances , let’s call it install_apache2.yaml would be:
- name: Update web servers
- name: Ensure Apache is at the latest version
As you can see the section hosts: in the YAML playbook matches the [ec2hosts] in your inventory file.
You can choose to have your private key certificate .pem file in /etc/ansible/ansible.cfg or if you want to have different certificates per host, add them after the ip/address in your inventory file, like in this example:
The first method is to use add_host to print in the screen the properties form the ec2 Instances provisioned.
The trick is to escape to shell, executing ansible-playbook and capturing the output, then parsing the text looking for the ‘public_ip:’
This is the Python 3 code I created:
def extract_public_ips_from_text(self, s_text=""):
Extracts the addresses returned by Ansible
:return: Boolean for success, Array with the Ip's
b_found = False
a_ips = 
i_count = 0
i_count += 1
if i_count > 20:
s_substr = "'public_ip': '"
i_first_pos = s_text.find(s_substr)
if i_first_pos > -1:
s_text_sub = s_text[i_first_pos + len(s_substr):]
# Find the ending delimiter
i_second_pos = s_text_sub.find("'")
if i_second_pos > -1:
b_found = True
s_ip = s_text_sub[0:i_second_pos]
s_text_sub = s_text_sub[i_second_pos:]
s_text = s_text_sub
# No more Ip's
return b_found, a_ips
Then you’ll use with something like:
# Catching the Ip's from the output
b_success, a_ips = self.extract_public_ips_from_text(s_output)
if b_success is True:
s_ips = ""
for s_ip in a_ips:
s_ips = s_ips + self.get_ip_text_line_for_inventory(s_ip)
print("Adding Ips to group1_inventory file")
The get_ip_text_line_for_inventory_method() returns a line for the inventory file, with the ip and the key to use separated by a tab (\t):
def get_ip_text_line_for_inventory(self, s_ip, s_key_path="ansible.pem"):
Returns the line to add to the inventory, with the Ip and the keypath
return s_ip + "\tansible_ssh_private_key_file=" + s_key_path + "\n"
Once you have the inventory file, like this below, you can execute the playbook for your group of hosts: