How Does a Python Docstring Work?

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Problem scenario
You know that Python has a feature for documentation strings that can print out when your program runs. How does it work as comments and as something that is displayed at the time the code is executed?

Solution
To best illustrate how one works, create a file called test.py with this code and run it:

def cool_function(n):
”’This is an example of a docstring. …

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How Do You Find the amd/i386 Architecture Indication for your Linux OS (to know what type of Debian Package you will need)?

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Problem scenario
You are trying to find out what .deb file you need (e.g., from pkgs.org). How do you find out if you need to decide between options like i386, arm, or amd64 on a Debian or Ubuntu server? What should you do?

Solution
Run this command:

sudo dpkg –print-architecture …

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How Do You Troubleshoot the Error “An error occurred (InvalidParameterException) when calling the CreateNodegroup operation: The provided nodeRole is invalid.”?

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Problem scenario
From the AWS CLI you try to create a node group. But you get this error: “An error occurred (InvalidParameterException) when calling the CreateNodegroup operation: The provided nodeRole is invalid.”

Solution
The above can happen when you use a role’s name but not the ARN string (such as arn:aws:iam::123456:role/foobar). Use the ARN string of the role instead of what you were using.

…

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How Do You Use Boto3 to Create EC-2 Instances?

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Problem scenario
You want to create EC-2 instances using an SDK (a program that automatically generates AWS resources). How do you do this?

Solution
Prerequisites
You have Boto3 installed. If you need assistance, see this posting if you have CentOS/RHEL/Fedora or this posting for Debian/Ubuntu.

Procedures
Run this program to create a RHEL server (but you can replace the “ami-0a54aef4ef3b5f881” with the image ID of your choice):

# Replace AKIAabcdefghijk with your AWS access key ID
# Replace 1a2b3c4d5e6f7g8h9/i0j0k9l8m7n6o5p4q3r2s1tuvwxyz with your AWS Secret Access key
# Replace us-west-1 with the region of your choice
# Replace ami-0a54aef4ef3b5f881 with the image ID of your choice. …

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What Is The Difference between Iterable and Subscriptable in Python?

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Question
You have seen messages when coding in Python about iterable and subscriptable. What is the difference between these two?

Answer
A subscriptable does not necessarily use the iter method, but an iterable always does.

A subscriptable object in Python leverages the getitem() method, but it may or may not use the iter method.

…

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How Do You Troubleshoot an apt Command That Has an Error “An error occurred during the signature verification”?

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Problem scenario
You are trying to run an apt command. It is failing. You get an error like this:

W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://repo.mongodb.org/apt/ubuntu…/foobar/1.1 Release: The following signatures were invalid: KEYEXPIRED 1507497109

What should you do?

Possible solution #1
This is not recommended.

…

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How Do You Find out which VPC Your Lambda Function Is In?

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Problem scenario
Some external requests that a Lambda function is making are not working. The Lambda logs indicate that the function is timing out. You want to see what VPC your Lambda function is in. What do you do?

Solution
Log into AWS via the web UI.
Go here (but change “us-west-1” in both places to your VPC’s region: https://us-west-1.console.aws.amazon.com/lambda/home?region=us-west-1#/functions/ )
Search for “VPC”
It may be that your Lambda function is not attached to any VPC.

…

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How Do You Troubleshoot dpkg Errors from apt Commands like “package post-installation script subprocess returned error exit status 1”?

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Problem scenario
On a Debian/Ubuntu server, you are trying to run apt commands. But you get errors like this:

dpkg: error processing package oracle-java11-installer-local (–configure):
installed oracle-java11-installer-local package post-installation script subprocess returned error exit status 1
Setting up nmap-common (7.80+dfsg1-2build1) …
Setting up liblua5.3-0:amd64 (5.3.3-1.1ubuntu2) …
dpkg: dependency problems prevent configuration of default-jre-headless:
default-jre-headless depends on openjdk-11-jre-headless; however:
Package openjdk-11-jre-headless is not installed.

…

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