A Tour of Tagging Schemas: Many-to-many, Bitmaps and More

april 03, 2015 09:59pm / peewee python sql / 0 comments

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In this post I'll describe how to implement tagging with a relational database. What I mean by tagging are those little labels you see at the top of this blog post, which indicate how I've chosen to categorize the content. There are many ways to solve this problem, and I'll try to describe some of the more popular methods, as well as one unconventional approach using bitmaps. In each section I'll describe the database schema, try to list the benefits and drawbacks, and present example queries. I will use Peewee ORM for the example code, but hopefully these examples will easily translate to your tool-of-choice.

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Meet Scout, a Search Server Powered by SQLite

march 28, 2015 11:03am / peewee python scout search sqlite / 5 comments

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In my continuing adventures with SQLite, I had the idea of writing a RESTful search server utilizing SQLite's full-text search extension. You might think of it as a poor man's ElasticSearch – a very, very poor man.

So what is this project? Well, the idea I had was that instead of building out separate search implementations for my various projects, I would build a single lightweight search service I could use everywhere. I really like SQLite (and have previously blogged about using SQLite's full-text search with Python), and the full-text search extension is quite good, so it didn't require much imagination to take the next leap and expose it as a web-service.

Read on for more details.

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How to make a Flask blog in one hour or less

march 09, 2015 08:43pm / flask peewee python / 1 comments

For fun, I thought I'd write a post describing how to build a blog using Flask, a Python web-framework. Building a blog seems like, along with writing a Twitter-clone, a quintessential experience when learning a new web framework. I remember when I was attending a five-day Django tutorial presented by Jacob Kaplan-Moss, one of my favorite projects we did was creating a blog. After setting up the core of the site, I spent a ton of time adding features and little tweaks here-and-there. My hope is that this post will give you the tools to build a blog, and that you have fun customizing the site and adding cool new features.

In this post we'll cover the basics to get a functional site, but leave lots of room for personalization and improvements so you can make it your own. The actual Python source code for the blog will be a very manageable 200 lines.

Who is this post for?

This post is intended for beginner to intermediate-level Python developers, or experienced developers looking to learn a bit more about Python and Flask. For the mother of all Flask tutorials, check out Miguel Grinberg's 18 part Flask mega-tutorial.

The spec

Here are the features:

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Querying the top N objects per group with Peewee ORM

march 03, 2015 12:39am / peewee python sql / 1 comments

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This post is a follow-up to my post about querying the top related item by group. In this post we'll go over ways to retrieve the top N related objects by group using the Peewee ORM. I've also presented the SQL and the underlying ideas behind the queries, so you can translate them to whatever ORM / query layer you are using.

Retrieving the top N per group is a pretty common task, for example:

In this post we'll discuss the following types of solutions:

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Querying the top item by group with peewee ORM

february 27, 2015 09:10pm / peewee python sql / 0 comments

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In this post I'd like to share some techniques for querying the top item by group using the Peewee ORM. For example,

This is a common task, but one that can be a little tricky to implement in a single SQL query. To add a twist, we won't use window functions or other special SQL constructs, since they aren't supported by SQLite. If you're interested in finding the top N items per group, check out this follow-up post.

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Managing Database Connections with Peewee

february 12, 2015 01:48am / peewee python / 0 comments

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Recently I've been receiving a lot of questions about how to manage database connections with the peewee ORM. I thought I'd write a short post explaining the various ways peewee can help you manage your database connections, and outline some general best practices.

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Naive Bayes Classifier using Python and Kyoto Cabinet

february 03, 2015 12:04am / kyotocabinet nosql python / 1 comments

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In this post I will describe how to build a simple naive bayes classifier with Python and the Kyoto Cabinet key/value database. I'll begin with a short description of how a probabilistic classifier works, then we will implement a simple classifier and put it to use by writing a spam detector. The training and test data will come from the Enron spam/ham corpora, which contains several thousand emails that have been pre-categorized as spam or ham.

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Walrus: Lightweight Python utilities for working with Redis

january 11, 2015 07:49pm / nosql python redis walrus / 5 comments

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A couple weekends ago I got it into my head that I would build a thin Python wrapper for working with Redis. Andy McCurdy's redis-py is a fantastic low-level client library with built-in support for connection-pooling and pipelining, but it does little more than provide an interface to Redis' built-in commands (and rightly so). I decided to build a project on top of redis-py that exposed pythonic containers for the Redis data-types. I went on to add a few extras, including a cache and a declarative model layer. The result is walrus.

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Setting up ElasticSearch with Basic Auth and SSL for use with Python

january 06, 2015 11:04pm / elasticsearch python / 7 comments

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I'm interested in learning to use ElasticSearch, so I thought I'd document how I set it up on my EC2 instance. Because I wanted to write code on my laptop, I needed to expose ElasticSearch over the public internet, which added a bit of extra complexity. Here is a rough outline of the process:

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Pollywog: Fun with Regular Expressions

december 30, 2014 05:03pm / pollywog python regex / 0 comments

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After writing about building a nicer regex API using operator overloading, I thought it would be fun to flesh out the code and release it as a library. I'm calling the result pollywog and you can find the code on GitHub.

To install pollywog, you can use pip or clone the GitHub repository:

$ pip install pollywog

In this post I'll show some examples of using pollywog.

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