Julien Danjou

Julien Danjou

Debugging C code on macOS

Debugging C code on macOS

I started to write C 25 years ago now, with many different tools over the year. As many open source developers, I spent most of my life working with the GNU tools out there. As I've been using an Apple computer over the last years, I had to adapt to

I am a Software Engineer and I am in Charge

I am a Software Engineer and I am in Charge

Fifteen years have passed since I started my career in IT — which is quite some time. I've been playing with computers for 25 years now, which makes me quite knowledgeable about the field, for sure. However, while I was fully prepared to bargain with computers, I was not prepared to

Interview: The Performance of Python

Interview: The Performance of Python

Earlier this year, I was supposed to participate to dotPy [https://dotpy.io], a one-day Python conference happening in Paris. This event has unfortunately been cancelled due to the COVID-19 pandemic. Both Victor Stinner and me were supposed to attend that event. Victor had prepared a presentation about Python performances,

Being in Charge

Being in Charge

If you never heard of the 10x engineer myth, it's a pretty great concept. It boils down to the idea where an engineer could be 10x more efficient than a random engineer. I find this fantastically twisted. Last week, I sat and chat with Alexis Monville in Le Podcast [https:

One year of Mergify

One year of Mergify

It has been close to a year now that I've incorporated my new company, Mergify [https://mergify.io]. I've been busy, and I barely wrote anything about it so far. Now is an excellent time to take a break and reflect a bit on what happened during those last 12

Attending FOSDEM 2020

Attending FOSDEM 2020

This weekend, I've been lucky to attend again the FOSDEM [https://fosdem.org/2020/] conference, one of the largest open-source conference out there. I had a talk scheduled in the Python devroom [https://fosdem.org/2020/schedule/track/python/] on Saturday about building a production-ready profiling in Python [https://fosdem.

Python Logging with Datadog

Python Logging with Datadog

At Mergify [https://mergify.io], we generate a pretty large amount of logs. Every time an event is received from GitHub for a particular pull request, our engine computes a new state for it. Doing so, it logs some informational statements about what it's doing — and any error that might

Atomic lock-free counters in Python

Atomic lock-free counters in Python

At Datadog [https://datadog.com], we're really into metrics. We love them, we store them, but we also generate them. To do that, you need to juggle with integers that are incremented, also known as counters. While having an integer that changes its value sounds dull, it might not be

Properly managing your .gitignore file

Properly managing your .gitignore file

There's not a single month where I don't have to explain this. I thought it'd be a good opportunity to write about this .gitignore file so everyone is up to date on this magic file. The purpose of .gitignore The .gitignore file is meant to be a list of files

Finding definitions from a source file and a line number in Python

Finding definitions from a source file and a line number in Python

My job at Datadog [https://datadog.com] keeps me busy with new and questioning challenges. I recently stumbled upon a problem that sounded easy but was more difficult than I imagined. Here's the thing: considering a filename and a line number, can you tell which function, method or class this

Sending Emails in Python — Tutorial with Code Examples

Sending Emails in Python — Tutorial with Code Examples

What do you need to send an email with Python? Some basic programming and web knowledge along with the elementary Python skills. I assume you’ve already had a web app built with this language and now you need to extend its functionality with notifications or other emails sending. This

Python and fast HTTP clients

Python and fast HTTP clients

Nowadays, it is more than likely that you will have to write an HTTP client for your application that will have to talk to another HTTP server. The ubiquity of REST API makes HTTP a first class citizen. That's why knowing optimization patterns are a prerequisite. There are many HTTP

Dependencies Handling in Python

Dependencies Handling in Python

Dependencies are a nightmare for many people. Some even argue they are technical debt [https://thenewstack.io/to-reduce-tech-debt-eliminate-dependencies-and-refactoring/] . Managing the list of the libraries of your software is a horrible experience. Updating them — automatically? — sounds like a delirium. Stick with me here as I am going to help you get

The Art of PostgreSQL is out!

The Art of PostgreSQL is out!

If you remember well, a couple of years ago, I wrote about Mastering PostgreSQL, a fantastic book written by my friend Dimitri Fontaine. Dimitri is a long-time PostgreSQL core developer — for example, he wrote the extension support in PostgreSQL — no less. He is featured in my book Serious Python [https:

Handling multipart/form-data natively in Python

Handling multipart/form-data natively in Python

RFC7578 [https://tools.ietf.org/html/rfc7578] (who obsoletes RFC2388 [https://tools.ietf.org/html/rfc2388]) defines the multipart/form-data type that is usually transported over HTTP when users submit forms on your Web page. Nowadays, it tends to be replaced by JSON encoded payloads; nevertheless, it is still widely

Advanced Functional Programming in Python: lambda

Advanced Functional Programming in Python: lambda

A few weeks ago, I introduced you to functional programming in Python [julien.danjou.info/python-and-functional-programming/]. Today, I'd like to go further into this topic and show you so more interesting features. Lambda Functions What do we call lambda functions? They are in essence anonymous functions. In order to create

An Introduction to Functional Programming with Python

An Introduction to Functional Programming with Python

Many Python developers are unaware of the extent to which you can use functional programming in Python, which is a shame: with few exceptions, functional programming allows you to write more concise and efficient code. Moreover, Python’s support for functional programming is extensive. Here I'd like to talk a

Writing Your Own Filtering DSL in Python

Writing Your Own Filtering DSL in Python

A few months ago, we've seen how to write a filtering syntax tree [https://julien.danjou.info/multi-value-syntax-tree-filtering-in-python/] in Python. The idea behind this was to create a data structure — in the form of a dictionary — that would allow to filter data based on conditions. Our API looked like this:

Python + Memcached: Efficient Caching in Distributed Applications

Python + Memcached: Efficient Caching in Distributed Applications

When writing Python applications, caching is important. Using a cache to avoid recomputing data or accessing a slow database can provide you with a great performance boost. Python offers built-in possibilities for caching, from a simple dictionary to a more complete data structure such as functools.lru_cache [https://docs.

How to Log Properly in Python

How to Log Properly in Python

Logging is one of the most underrated features. Often ignored by software engineers, it can save your time when your application's running in production. Most teams don't think about it until it's too late in their development process. It's when things start to get wrong in deployments that somebody realizes

Serious Python released!

Serious Python released!

Today I'm glad to announce that my new book, Serious Python, has been released. However, you wonder… what is Serious Python? Well, Serious Python is the the new name of The Hacker's Guide to Python — the first book I published. Serious Python is the 4th update of that book — but

Why You Should Care That Your SQL DDL is Transactional

Why You Should Care That Your SQL DDL is Transactional

I don't write a lot about database management. How come? I'm a software engineer, and like many of my peers, I leverage databases to store data. I should talk more about this! What made me write this today is that I've discovered that many of my peers wouldn't be able

Podcast.__init__: Gnocchi, a Time Series Database for your Metrics

Podcast.init: Gnocchi, a Time Series Database for your Metrics

A few weeks ago, Tobias Macey contacted me as he wanted to talk about Gnocchi, the time series database I've been working on for the last few years. It was a great opportunity to talk about the project, so I jumped on it! We talk about how Gnocchi came to

A multi-value syntax tree filtering in Python

A multi-value syntax tree filtering in Python

A while ago, we've seen how to write a simple filtering syntax tree with Python [https://julien.danjou.info/simple-filtering-syntax-tree-in-python/]. The idea was to provide a small abstract syntax tree with an easy to write data structure that would be able to filter a value. Filtering meaning that once evaluated,

The Best flake8 Extensions for your Python Project

The Best flake8 Extensions for your Python Project

In the last blog post about coding style [https://julien.danjou.info/code-style-checks-in-python/], we dissected what the state of the art was regarding coding style check in Python. As we've seen, Flake8 is a wrapper around several tools and is extensible via plugins: meaning that you can add your own