How Do You Create a Class for Objects with Many Data Members and Access One Specific Data Member in Groovy?

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Problem scenario
You want to use Groovy to create a class and an object that is composed of many individual member data types.  How do you do this and access an individual data type of the object?

Solution
This Groovy program creates two objects from the same class using different syntax.  One method uses syntax “[]” and another method uses the “new” keyword.

@groovy.transform.Canonical
class Program {
    String mem1 = “”
    String mem2 = “”
    String mem3 = “”
    String mem4 = “”
    String mem5 = “”
    String mem6 = “”
    String mem7 = “”
    String mem8 = “”
    String mem9 = “”
}

programsv1 = new Program( “1”, …

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How Do You Troubleshoot the AWS CLI Error “Traceback … import pkg_resources”?

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Problem scenario
You run an “aws” command but you receive an error message such as this:

Traceback (most recent call last):
  File “/usr/bin/aws”, line 4, in <module>
    import pkg_resources
  File “/usr/lib/python2.7/site-packages/pkg_resources.py”, line 3007, in <module>

What should you do?

Solution
1.  Install pip.  If you need assistance, see this posting (especially the “Problem scenario” paragraph with hyperlinks based on distribution families of Linux).

…

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How Do You Troubleshoot the Error “intx ThreadPriorityPolicy=42 is outside the allowed range [ 0 … 1 ] “?

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Problem scenario
You try to start Cassandra but you get this error:

“[0.000s][warning][gc] -Xloggc is deprecated. Will use -Xlog:gc:./bin/../logs/gc.log instead.
intx ThreadPriorityPolicy=42 is outside the allowed range [ 0 … 1 ]
Improperly specified VM option ‘ThreadPriorityPolicy=42’
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.”

Possible solution #1
Migrate to Linux SUSE or a Red Hat family version of Linux (e.g.,

…

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How Do You Use a Generator and the Yield Keyword in Python?

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Problem scenario
You want to use a generator in Python.  You also want to use the yield keyword in Python.  How do you use these?

Solution
The short answer to the question about how do you use a generator is to create a function with the yield keyword (source Programiz.com).  “Both yield and return will return some value from a function.”  (The source of this quote is 

…

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How Do You Create Your Own Dockerfile to Create a Flask Application?

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Problem scenario
You want to use Flask inside a Docker container.  You want to build your own image for the Docker container.  How do you create your own Dockerfile to create a Flask application?

Solution
Prerequisite
Install Docker.  See this posting if you need directions.

Procedures
1.  Create a Dockerfile with the following content (you may want to replace “16.04” with “latest” and if you want to change the location of where the .py file is,

…

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How Do You Use GCP’s App Engine?

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Problem scenario
You want to leverage GCP’s serverless App Engine component with its scalability.  What do you do?

Solution
1.  Go to the cloud shell.  In the web UI of GCP in the upper righthand corner go to the icon that looks like this: “>_” and click on it.  From cloud shell run these commands:

git clone https://github.com/GoogleCloudPlatform/python-docs-samples

cd python-docs-samples/appengine/standard_python37/hello_world

virtualenv –python python3 ~/envs/hello_world

source ~/envs/hello_world/bin/activate

pip install -r requirements.txt

python main.py

2. 

…

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How Do You Create a Docker Image That Has Java 10 in It?

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Problem scenario
You want to create Docker containers with Java 9.  How do you create a Docker image to make containers with Java 9 installed in them?

These directions were updated on 12/26/18.

Solution
Prerequisite
This assumes that you have Docker installed. If you need assistance with this, see these postings depending on your operating system:

Debian/Ubuntu
CentOS/Fedora/RHEL
SUSE

Procedures
1. 

…

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How Do You Write a BubbleSort Algorithm in Python That Runs in O(n) in a Best Case Scenario?

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Problem scenario
You want to use BubbleSort in Python that runs in O(n) time when the list to be sorted is already in perfect order.  How do you write such a program?

Solution
Use this code for BubbleSort with a refinement:

def refinedBubbleSort(coollist):
needtoswap = True
x = len(coollist)-1 # x is now the index value of last item in list
while x 0 and needtoswap:
needtoswap = False
for i in range(x): # start with leftmost number and iterate to the xth position one space at a time
if coollist[i] coollist[i+1]: # swap if left item in pair is greater than right item
needtoswap = True
coollist[i],coollist[i+1] = coollist[i+1],coollist[i]
x = x-1 # Go through the list from rightmost item until the leftmost item
coollist = [1,2,3,4,5,6,7,8,9,10]
refinedBubbleSort(coollist)
print(coollist) …

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How Do You Write a Java Program to Accept Text from the Command Terminal and Print It Back Out?

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Problem scenario
You want to write a basic Java program to test it out.  How do you write a program to accept user input, specifically a alphanumeric input, and print it back to the screen?

Solution
1.  Install the Java Development Kit if you have not installed it yet.  If you are not sure you have it, run “javac -version“.  If it says that the command is not found,

…

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In Python, How Do You Call an Unbound Function as a New Thread with the thread Module?

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Problem scenario
You want to write a program to call a unbound function in a new thread with the threading module. How do you do this?

Solution
Run this program (e.g., python foobar.py):

import _thread as thread
def contint():
print(“Hello!”)

#if name == “main”:
foobar = thread.start_new_thread(contint, () )
print(“thread finished exiting”) …

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