Entries tagged with python
Task queues are frequently deployed alongside websites to do background processing outside the normal request/response cycle. In the past I've used them for things like sending emails, generating thumbnails, warming caches, or periodically fetching remote resources. By pushing that work out of the request/response cycle, you can increase the throughput (and responsiveness) of your web application.
Depending on your workload, though, it may be possible to move your task processing into the same process as your web server. In this post I'll describe how I did just that using gevent, though the technique would probably work well with a number of different WSGI servers.
In this post I'd like to share with you some techniques for effectively working with SQLite using Python. SQLite is a capable library, providing an in-process relational database for efficient storage of small-to-medium-sized data sets. It supports most of the common features of SQL with few exceptions. Best of all, most Python users do not need to install anything to get started working with SQLite, as the standard library in most distributions ships with the sqlite3 module.
Python3 is a mess. How did this happen? So many of the changes seem to me to fly in the face of the whole Zen of Python aesthetic. The two biggest offenders, in my opinion, are asyncio and type hints.
SQLite's write lock and pysqlite's clunky transaction state-machine are a toxic combination for multi-threaded applications. Unless you are very diligent about keeping your write transactions as short as possible, you can easily wind up with one thread accidentally holding a write transaction open for an unnecessarily long time. Threads that are waiting to write will then have a much greater likelihood of timing out while waiting for the lock, giving the illusion of poor performance.
In this post I'd like to share a very effective technique for performing writes to a SQLite database from multiple threads.
In this post I'll share a simple code snippet you can use to perform optimistic locking when updating model instances. I've intentionally avoided providing an implementation for this in peewee, because I don't believe it will be easy to find a one-size-fits-all approach to versioning and conflict resolution. I've updated the documentation to include the sample implementation provided here, however.
It's been over 2 years since I wrote about the tooling I use to theme my desktop, so I thought I'd post about my current scripts...
When Kenneth Reitz created the
requests library, the Python community rushed to embrace the project, as it provided (finally) a clean, sane API for making HTTP requests. He subtitled his project "Python HTTP Requests for Humans", referring, I suppose, to the fact that his API provided developer-friendly APIs. If naming things "for humans" had stopped there, that would have been fine with me, but instead there's been a steady stream of new projects describing themselves as being "For Humans" and I have issues with that.
If you haven't heard, SQLite is an amazing database capable of doing real work in real production environments. In this post, I'll outline 5 reasons why I think you should use SQLite in 2016.
Sophia is a powerful key/value database with loads of features packed into a simple C API. In order to use this database in some upcoming projects I've got planned, I decided to write some Python bindings and the result is sophy. In this post, I'll describe the features of Sophia database, and then show example code using
sophy, the Python wrapper.
Here is an overview of the features of the Sophia database:
- Append-only MVCC database
- ACID transactions
- Consistent cursors
- Ordered key/value store
- Range searches
- Prefix searches
One of the benefits of running an embedded database like SQLite is that you can configure SQLite to call into your application's code. SQLite provides APIs that allow you to create your own scalar functions, aggregate functions, collations, and even your own virtual tables. In this post I'll describe how I used the virtual table APIs to expose a nice API for creating table-valued (or, multi-value) functions in Python. The project is called
sqlite-vtfunc and is hosted on GitHub. If you use Peewee, an equivalent implementation is included in the Peewee SQLite extensions.