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Linux Mastering Development Ubuntu

UBUNTU 20.04 LTS. Can’t run updates. Says version unsupported

I did the upgrade to 20.04 about 4 months ago. I downloaded it from the page that kept sending me upgrade messages, and did a fresh install on my new SSD. All worked well, updating software multiple times in the past few months from South African servers. I am now in North Africa. I tried […]

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Mastering Development

Allow reserved key words as methods in CPython

It looks like Python has a list of reserved key words that cannot be used as method names. For instance, class A: def finally(self): return 0 returns a SyntaxError: invalid syntax. There is a way around it with getattr/setattr, class A: pass setattr(A, ‘finally’, lambda self: 0) a = A() print(getattr(a, "finally")()) works fine. However, […]

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User Help

How to install Keras ad Tensorflow in R?

I’m trying to install keras and tensorflow packages in R, but everytime I do this I experience problems and difficulties and,finally, fail. First, I do: install.packages ("keras") I get: `Installing package into ‘C:/Users/user/Documents/R/win-library/4.0’ (as ‘lib’ is unspecified) trying URL ‘https://cran.rstudio.com/bin/windows/contrib/4.0/keras_2.3.0.0.zip’ Content type ‘application/zip’ length 2488234 bytes (2.4 MB) downloaded 2.4 MB package ‘keras’ successfully unpacked […]

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Mastering Development

How to merge 2 tables based on values

Let say, I have 2 tables – Table 1 : +——+——+——+——+ | Col1 | Col2 | Col3 | Col4 | +——+——+——+——+ | 2 | A | 10 | X | | 3 | B | 23 | Y | | 2 | C | 11 | X | | 5 | D | 34 | […]

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Linux Mastering Development Ubuntu

Unable to record audio even with all working amixer controls | thinkpad t430

I have a T430 thinkpad, and it is unable to record audio. Details follow : What I am trying to do: All I am trying to do is, get my laptop’s microphone in working state. I am trying this with the default-system-microphone, as well as with the headset that I have (single 3.5mm jack with […]

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Mastering Development

when zookeeper shutdown,zkDb invoke the method fastForwardDataBase(), this method add transactions from the committed log into memory

i have a question about this,e.g.,there are five node in a cluster, if leader crash and not send a commit order,and only one follower receive the proposal and sync to disk,finally,this proposal is success or fail ? /** * Fast forward the database adding transactions from the committed log into memory. * @return the last […]

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Ask Chemistry

Grasping the concept of Electronic Spin, Effective Spin and Fictitious Spin

Trying to learn alone some aspects of quantum mechanics is, sometimes, a struggle. Reading the excellent paper by Piwowarska (DOI 10.1007/s00723-018-1080-4) I was hoping to, finally, understand what is the origin of the so-called “fictitious spin $1/2$” in a $\mathrm d^7$ cobalt ion. If my cobalt is high spin ($3/2$ is the electronic spin $S$), […]

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Ask Chemistry

Grasping the concept of Electronic Spin, Effective Spin and Fictitious Spin

Trying to learn alone some aspects of quantum mechanics is, sometimes, a struggle. Reading the excellent paper by Piwowarska (DOI 10.1007/s00723-018-1080-4) I was hoping to, finally, understand what is the origin of the so-called “fictitious spin $1/2$” in a $\mathrm d^7$ cobalt ion. If my cobalt is high spin ($3/2$ is the electronic spin $S$), […]

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CMS Drupal Mastering Development

Access Denied when visiting my custom route

I have a custom module with machine name "mymodule". The mymodule.info.yml file looks like this: name: My module type: module description: ‘My first drupal module’ core: 8.x Then I have a src/Controller/FirstController.php which looks like: <?php namespace Drupal\mymodule\Controller; use Drupal\Core\Controller\ControllerBase; /** * Defines FirstController class. */ class FirstController extends ControllerBase { /** * Display the […]

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Mastering Development System & Network

vsftp has a bug with Fedora 32 – how do I report it: 500 OOPS: SSL: cannot load RSA private key vsftpd

Just to be clear, this is as of Fedora 32, and vsftpd-3.0.3-36.fc32.x86_64 for vsftpd. This is NOT the same problem as previously was reported here, but it has the same outward appearance and, indeed, the answer(s) there were helpful in my figuring out there are bugs worthy of reporting which I haven’t yet figured out […]