30 Oct 2020

feedPlanet Python

NumFOCUS: Public Apology to Jeremy Howard

We, the NumFOCUS Code of Conduct Enforcement Committee, issue a public apology to Jeremy Howard for our handling of the JupyterCon 2020 reports. We should have done better. We thank you for sharing your experience and we will use it to improve our policies going forward. We acknowledge that it was an extremely stressful experience, […]

The post Public Apology to Jeremy Howard appeared first on NumFOCUS.

30 Oct 2020 6:51pm GMT

PythonClub - A Brazilian collaborative blog about Python: Fazendo backup do banco de dados no Django

Apresentação

Em algum momento, durante o seu processo de desenvolvimento com Django, pode ser que surja a necessidade de criar e restaurar o banco de dados da aplicação. Pensando nisso, resolvi fazer um pequeno tutorial, básico, de como realizar essa operação.

Nesse tutorial, usaremos o django-dbbackup, um pacote desenvolvido especificamente para isso.

Configurando nosso ambiente

Primeiro, partindo do início, vamos criar uma pasta para o nosso projeto e, nela, isolar o nosso ambiente de desenvolvimento usando uma virtualenv:

mkdir projeto_db && cd projeto_db #criando a pasta do nosso projeto

virtualenv -p python3.8 env && source env/bin/activate #criando e ativando a nossa virtualenv

Depois disso e com o nosso ambiente já ativo, vamos realizar os seguintes procedimentos:

pip install -U pip #com isso, atualizamos a verão do pip instalado

Instalando as dependências

Agora, vamos instalar o Django e o pacote que usaremos para fazer nossos backups.

pip install Django==3.1.2 #instalando o Django

pip install django-dbbackup #instalando o django-dbbackup

Criando e configurando projeto

Depois de instaladas nossas dependências, vamos criar o nosso projeto e configurar o nosso pacote nas configurações do Django.

django-admin startproject django_db . #dentro da nossa pasta projeto_db, criamos um projeto Django com o nome de django_db.

Depois de criado nosso projeto, vamos criar e popular o nosso banco de dados.

python manage.py migrate #com isso, sincronizamos o estado do banco de dados com o conjunto atual de modelos e migrações.

Criado nosso banco de dados, vamos criar um superusuário para podemos o painel admin do nosso projeto.

python manage.py createsuperuser

Perfeito. Já temos tudo que precisamos para executar nosso projeto. Para execução dele, é só fazermos:

python manage.py runserver

Você terá uma imagem assim do seu projeto:

Configurando o django-dbbackup

Dentro do seu projeto, vamos acessar o arquivo settings.py, como expresso abaixo:

django_db/
├── settings.py

Dentro desse arquivos iremos, primeiro, adiconar o django-dbbackup às apps do projeto:

INSTALLED_APPS = (
    ...
    'dbbackup',  # adicionando django-dbbackup
)

Depois de adicionado às apps, vamos dizer para o Django o que vamos salvar no backup e, depois, indicar a pasta para onde será encaminhado esse arquivo. Essa inserção deve ou pode ser feita no final do arquivo settings.py:

DBBACKUP_STORAGE = 'django.core.files.storage.FileSystemStorage' #o que salvar
DBBACKUP_STORAGE_OPTIONS = {'location': 'backups/'} # onde salvar

Percebam que dissemos para o Django salvar o backup na pasta backups, mas essa pasta ainda não existe no nosso projeto. Por isso, precisamos criá-la [fora da pasta do projeto]:

mkdir backups

Criando e restaurando nosso backup

Já temos tudo pronto. Agora, vamos criar o nosso primeiro backup:

python manage.py dbbackup

Depois de exetudado, será criado um arquivo -- no nosso exemplo, esse arquivo terá uma extensão .dump --, salvo na pasta backups. Esse arquivo contem todo backup do nosso banco de dados.

Para recuperarmos nosso banco, vamos supor que migramos nosso sistema de um servidor antigo para um novo e, por algum motivo, nossa base de dados foi corrompida, inviabilizando seu uso. Ou seja, estamos com o sistema/projeto sem banco de dados -- ou seja, exlua ou mova a a sua base dados .sqlite3 para que esse exemplo seja útil --, mas temos os backups. Com isso, vamos restaurar o banco:

python manage.py dbrestore

Prontinho, restauramos nosso banco de dados. O interessante do django-dbbackup, dentre outras coisas, é que ele gera os backups com datas e horários específicos, facilitando o processo de recuperação das informações mais recentes.

Por hoje é isso, pessoal. Até a próxima. ;)

30 Oct 2020 1:40pm GMT

Real Python: The Real Python Podcast – Episode #33: Going Beyond the Basic Stuff With Python and Al Sweigart

You probably have heard of the bestselling Python book, "Automate the Boring Stuff with Python." What are the next steps after starting to dabble in the Python basics? Maybe you've completed some tutorials, created a few scripts, and automated repetitive tasks in your life. This week on the show, we have author Al Sweigart to talk about his new book, "Beyond the Basic Stuff with Python: Best Practices for Writing Clean Code."


[ Improve Your Python With 🐍 Python Tricks 💌 - Get a short & sweet Python Trick delivered to your inbox every couple of days. >> Click here to learn more and see examples ]

30 Oct 2020 12:00pm GMT

10 Nov 2011

feedPlanetJava

OSDir.com - Java: Oracle Introduces New Java Specification Requests to Evolve Java Community Process

From the Yet Another dept.:

To further its commitment to the Java Community Process (JCP), Oracle has submitted the first of two Java Specification Requests (JSRs) to update and revitalize the JCP.

10 Nov 2011 6:01am GMT

OSDir.com - Java: No copied Java code or weapons of mass destruction found in Android

From the Fact Checking dept.:

ZDNET: Sometimes the sheer wrongness of what is posted on the web leaves us speechless. Especially when it's picked up and repeated as gospel by otherwise reputable sites like Engadget. "Google copied Oracle's Java code, pasted in a new license, and shipped it," they reported this morning.



Sorry, but that just isn't true.

10 Nov 2011 6:01am GMT

OSDir.com - Java: Java SE 7 Released

From the Grande dept.:

Oracle today announced the availability of Java Platform, Standard Edition 7 (Java SE 7), the first release of the Java platform under Oracle stewardship.

10 Nov 2011 6:01am GMT

28 Oct 2011

feedPlanet Ruby

O'Reilly Ruby: MacRuby: The Definitive Guide

Ruby and Cocoa on OS X, the iPhone, and the Device That Shall Not Be Named

28 Oct 2011 8:00pm GMT

14 Oct 2011

feedPlanet Ruby

Charles Oliver Nutter: Why Clojure Doesn't Need Invokedynamic (Unless You Want It to be More Awesome)

This was originally posted as a comment on @fogus's blog post "Why Clojure doesn't need invokedynamic, but it might be nice". I figured it's worth a top-level post here.

Ok, there's some good points here and a few misguided/misinformed positions. I'll try to cover everything.

First, I need to point out a key detail of invokedynamic that may have escaped notice: any case where you must bounce through a generic piece of code to do dispatch -- regardless of how fast that bounce may be -- prevents a whole slew of optimizations from happening. This might affect Java dispatch, if there's any argument-twiddling logic shared between call sites. It would definitely affect multimethods, which are using a hand-implemented PIC. Any case where there's intervening code between the call site and the target would benefit from invokedynamic, since invokedynamic could be used to plumb that logic and let it inline straight through. This is, indeed, the primary benefit of using invokedynamic: arbitrarily complex dispatch logic folds away allowing the dispatch to optimize as if it were direct.

Your point about inference in Java dispatch is a fair one...if Clojure is able to infer all cases, then there's no need to use invokedynamic at all. But unless Clojure is able to infer all cases, then you've got this little performance time bomb just waiting to happen. Tweak some code path and obscure the inference, and kablam, you're back on a slow reflective impl. Invokedynamic would provide a measure of consistency; the only unforeseen perf impact would be when the dispatch turns out to *actually* be polymorphic, in which case even a direct call wouldn't do much better.

For multimethods, the benefit should be clear: the MM selection logic would be mostly implemented using method handles and "leaf" logic, allowing hotspot to inline it everywhere it is used. That means for small-morphic MM call sites, all targets could potentially inline too. That's impossible without invokedynamic unless you generate every MM path immediately around the eventual call.

Now, on to defs and Var lookup. Depending on the cost of Var lookup, using a SwitchPoint-based invalidation plus invokedynamic could be a big win. In Java 7u2, SwitchPoint-based invalidation is essentially free until invalidated, and as you point out that's a rare case. There would essentially be *no* cost in indirecting through a var until that var changes...and then it would settle back into no cost until it changes again. Frequently-changing vars could gracefully degrade to a PIC.

It's also dangerous to understate the impact code size has on JVM optimization. The usual recommendation on the JVM is to move code into many small methods, possibly using call-through logic as in multimethods to reuse the same logic in many places. As I've mentioned, that defeats many optimizations, so the next approach is often to hand-inline logic everywhere it's used, to let the JVM have a more optimizable view of the system. But now we're stepping on our own feet...by adding more bytecode, we're almost certainly impacting the JVM's optimization and inlining budgets.

OpenJDK (and probably the other VMs too) has various limits on how far it will go to optimize code. A large number of these limits are based on the bytecoded size of the target methods. Methods that get too big won't inline, and sometimes won't compile. Methods that inline a lot of code might not get inlined into other methods. Methods that inline one path and eat up too much budget might push out more important calls later on. The only way around this is to reduce bytecode size, which is where invokedynamic comes in.

As of OpenJDK 7u2, MethodHandle logic is not included when calculating inlining budgets. In other words, if you push all the Java dispatch logic or multimethod dispatch logic or var lookup into mostly MethodHandles, you're getting that logic *for free*. That has had a tremendous impact on JRuby performance; I had previous versions of our compiler that did indeed infer static target methods from the interpreter, but they were often *slower* than call site caching solely because the code was considerably larger. With invokedynamic, a call is a call is a call, and the intervening plumbing is not counted against you.

Now, what about negative impacts to Clojure itself...

#0 is a red herring. JRuby supports Java 5, 6, and 7 with only a few hundred lines of changes in the compiler. Basically, the compiler has abstract interfaces for doing things like constant lookup, literal loading, and dispatch that we simply reimplement to use invokedynamic (extending the old non-indy logic for non-indified paths). In order to compile our uses of invokedynamic, we use Rémi Forax's JSR-292 backport, which includes a "mock" jar with all the invokedynamic APIs stubbed out. In our release, we just leave that library out, reflectively load the invokedynamic-based compiler impls, and we're off to the races.

#1 would be fair if the Oracle Java 7u2 early-access drops did not already include the optimizations that gave JRuby those awesome numbers. The biggest of those optimizations was making SwitchPoint free, but also important are the inlining discounting and MutableCallSite improvements. The perf you see for JRuby there can apply to any indirected behavior in Clojure, with the same perf benefits as of 7u2.

For #2, to address the apparent vagueness in my blog post...the big perf gain was largely from using SwitchPoint to invalidate constants rather than pinging a global serial number. Again, indirection folds away if you can shove it into MethodHandles. And it's pretty easy to do it.

#3 is just plain FUD. Oracle has committed to making invokedynamic work well for Java too. The current thinking is that "lambda", the support for closures in Java 7, will use invokedynamic under the covers to implement "function-like" constructs. Oracle has also committed to Nashorn, a fully invokedynamic-based JavaScript implementation, which has many of the same challenges as languages like Ruby or Python. I talked with Adam Messinger at Oracle, who explained to me that Oracle chose JavaScript in part because it's so far away from Java...as I put it (and he agreed) it's going to "keep Oracle honest" about optimizing for non-Java languages. Invokedynamic is driving the future of the JVM, and Oracle knows it all too well.

As for #4...well, all good things take a little effort :) I think the effort required is far lower than you suspect, though.

14 Oct 2011 2:40pm GMT

07 Oct 2011

feedPlanet Ruby

Ruby on Rails: Rails 3.1.1 has been released!

Hi everyone,

Rails 3.1.1 has been released. This release requires at least sass-rails 3.1.4

CHANGES

ActionMailer

ActionPack

ActiveModel

ActiveRecord

ActiveResource

ActiveSupport

Railties

SHA-1

You can find an exhaustive list of changes on github. Along with the closed issues marked for v3.1.1.

Thanks to everyone!

07 Oct 2011 5:26pm GMT

21 Mar 2011

feedPlanet Perl

Planet Perl is going dormant

Planet Perl is going dormant. This will be the last post there for a while.

image from planet.perl.org

Why? There are better ways to get your Perl blog fix these days.

You might enjoy some of the following:

Will Planet Perl awaken again in the future? It might! The universe is a big place, filled with interesting places, people and things. You never know what might happen, so keep your towel handy.

21 Mar 2011 2:04am GMT

improving on my little wooden "miniatures"

A few years ago, I wrote about cheap wooden discs as D&D minis, and I've been using them ever since. They do a great job, and cost nearly nothing. For the most part, we've used a few for the PCs, marked with the characters' initials, and the rest for NPCs and enemies, usually marked with numbers.

With D&D 4E, we've tended to have combats with more and more varied enemies. (Minions are wonderful things.) Numbering has become insufficient. It's too hard to remember what numbers are what monster, and to keep initiative order separate from token numbers. In the past, I've colored a few tokens in with the red or green whiteboard markers, and that has been useful. So, this afternoon I found my old paints and painted six sets of five colors. (The black ones I'd already made with sharpies.)

D&D tokens: now in color

I'm not sure what I'll want next: either I'll want five more of each color or I'll want five more colors. More colors will require that I pick up some white paint, while more of those colors will only require that I re-match the secondary colors when mixing. I think I'll wait to see which I end up wanting during real combats.

These colored tokens should work together well with my previous post about using a whiteboard for combat overview. Like-type monsters will get one color, and will all get grouped to one slot on initiative. Last night, for example, the two halfling warriors were red and acted in the same initiative slot. The three halfling minions were unpainted, and acted in another, later slot. Only PCs get their own initiative.

I think that it did a good amount to speed up combat, and that's even when I totally forgot to bring the combat whiteboard (and the character sheets!) with me. Next time, we'll see how it works when it's all brought together.

21 Mar 2011 12:47am GMT

20 Mar 2011

feedPlanet Perl

Perl Vogue T-Shirts

Is Plack the new Black?In Pisa I gave a lightning talk about Perl Vogue. People enjoyed it and for a while I thought that it might actually turn into a project.

I won't though. It would just take far too much effort. And, besides, a couple of people have pointed out to be that the real Vogue are rather protective of their brand.

So it's not going to happen, I'm afraid. But as a subtle reminder of the ideas behind Perl Vogue I've created some t-shirts containing the article titles from the talk. You can get them from my Spreadshirt shop.

20 Mar 2011 12:02pm GMT