yujia21

Watching my cats with a Pi, a webcam, and Tailscale

Mon, 01 Jun 2026 00:00:00 +0000

I have been meaning to set up a pet cam to watch my two cats for a while, and finally had some free time to get around to doing it. Since I have an old USB webcam, a Raspberry Pi that was lying around doing nothing, I decided to set up something with my existing hardware rather than buying something off the shelf.

Functionalities desired

Have a live view of my living room from my phone or from my laptop
Use existing hardware: a USB webcam and Raspberry Pi 4 Model B
Nothing accessible from an unknown phone or laptop

I had considered setting up a system where motion is started only if someone is actively requesting a view, instead of the USB camera being on all the time, but the energy saved did not seem worth it as the Pi would be on all the time anyway.

Writing a Sans-IO Python library for BACnet in Rust

Fri, 01 May 2026 00:00:00 +0000

With the advent of AI tools for coding, random side projects that used to live in my head finally see the light of day.

I’ve primarily been playing around with opencode for my personal use, an AI coding agent which by default has both a planning and building mode.

Rust and Python

For a while, I’ve been meaning to understand how to publish libraries for Python written in Rust. The significant speed-up provided by compute heavy libraries written in Rust such as pydantic, ruff, and uv has significantly changed the landscape of Python tools.

Multi-tasking with Python

Mon, 01 Apr 2024 00:00:00 +0000

In 2024 I gave an introductory talk at the Python User Group Singapore on the topic of asynchronous programming in Python.

The recording can be found here and the demo repository here

Recent resale flat sales

Sat, 13 Nov 2021 00:00:00 +0000

Dataset

Dataset retrieved as usual from Singapore’s public data. Only data after 2017, in the towns of Queenstown, Bukit Merah, and Clementi are displayed in the graph below.

Interactive graph

(This has been removed temporarily as it is too large)

Process

Data cleanup
Learning basic JavaScript to write callbacks to filter dataset in Bokeh graph, inspiration here
Not the most optimized and will be slow to reload due to having to loop through dataset with the filter

Learning to play Can't Stop with a Deep Q Network

Wed, 20 May 2020 00:00:00 +0000

What with the COVID19 related confinement, I have been playing a lot of board games on board game arena with friends, colleagues, you name it. When you first create an account, the site takes you through the tutorial of a simple probabilistic risk vs gain evaluation game called Can’t Stop. Having a little more time on my hands during weekends than usual, I decided to train a reinforcement learning agent to learn to play this game, for which the full code can be found here.

What data does TraceTogether really track?

Fri, 10 Apr 2020 00:00:00 +0000

TraceTogether

In the midst of the COVID19 crisis, the Singapore government has developed an app called TraceTogether, on which much ink has already been spilt. The goal of the app is to aid in contact tracing by keeping track of people you might come into close contact with unknowingly (for example, on the train, at a hawker center) via tracking bluetooth signals. I won’t go into more detail on how the app works or on privacy concerns since those are not really my areas of “expertise”, but merely be content with examining the data collected in my TraceTogether app.

Which boat should my rowing club buy?

Sun, 15 Mar 2020 00:00:00 +0000

Dataset

As one of the resident data scientists of my rowing club, I decided to play a little with the data generated by boat booking over the year 2019. Data was collected from a shared online Google Sheets file, where members wrote down their names for the boat they intended to use and the date/time where they were rowing. Since this analysis was done, stricter logging policies were implemented (standardizing names used by members by forcing the choice to be made from a drop down list, and enforcing full list of crew names for crew boats), so next year’s of data analysis should be less painful! Of course, this dataset doesn’t take into account those with private single boats - they appear on the sheet only when they row in crew boats.

How much does it rain in Singapore?

Sun, 15 Sep 2019 00:00:00 +0000

Dataset

Real time weather data can be retrieved from this API provided by NEA and the Singapore government and is available for free. We have air temperature, rainfall, windspeed, and wind direction data.

Data can only be fetched day by day or for a specific timestep through this API. It is pretty simple to write a quick script to request data from the API using Python’s “requests” library. Data is returned in json format and subsequently converting the data into a pandas dataframe just takes a little more work (a naive conversion into a dataframe results in two columns: one for the timestamp and one where the entry for each timestep is a list of dictionaries of the form {“sensor id”: xx, “value”, yy}).

What do Singapore's electricity prices look like?

Sat, 31 Aug 2019 00:00:00 +0000

Dataset

The following data is retrieved from the Energy Market Company website and is available for free.

This dataset comprises of the 2018 Uniform Singapore Energy Price (USEP) as well as the overall demand in Singapore in MW, among other variables that are not shown below. Data is available in half hourly periods. The USEP is here in $/MWh, and is determined by the demand and supply of the electricity market of the period in question.

About

Mon, 01 Jan 0001 00:00:00 +0000

yujia21: 于佳 (yu2 jia1)
Based in Singapore
Keeping 2 cats alive
Currently working as a Software Engineer at Zenika. Previously at BeeBryte.

Poetry

Mon, 01 Jan 0001 00:00:00 +0000

In my free time, I dabble in poetry.

My work has been published in the following:

Monday
- QLRS Vol. 18 No. 3 Jul 2019
Evening at Dakota Crescent
- QLRS Vol. 19 No. 1 Jan 2020
- Little Things: An Anthology of Poetry, Ethos
Plaintains
- QLRS Vol. 24 No. 3 Jul 2025
We choose a neighbourhood
- QLRS Vol. 25 No. 2 Apr 2026

Websites

Mon, 01 Jan 0001 00:00:00 +0000

Here are some websites or web apps I have built.

Gai Gai - an SG bus arrival app that knows your weekly schedule
Easter Rowing Club - static website for my rowing club