Sister Cities

This post is on so called “sister cities”, also called “twin towns”; where towns form symbolic partnerships with other towns. I was wondering how connected towns are through this bond: Is it possible to start at one town, go to one of its sister cities, then one of its sister cities, and so on, to eventually reach any other city.

To test this, I used WikiData, which conveniently has a property type for sister cities (P190). I ignored the API documentation, but found the basic entity request URL for my hometown.

In it, I searched for P190 and found a list of entities, all refering to partner cities of Weimar. Then I stopped with doing things manually and wrote a short Python script to recursively crawl all towns “reachable” from my starting point.

A few hours later, I had a list of about 34k links between towns (in both directions). I also saved the names of the cities, so I didn’t have to look at the WikiData IDs. Afterwards, I wrote a quick&dirty script to explore sister cities interactively.

The network seems to be pretty well connected, probably because:

• Horizontally: Big cities are linked to eachother. They also often have a high amount of connections, making them link smaller subnetworks.
• Vertically: Links aren’t always between exqually sized cities, which ensures that also the smallest towns have a connection to the big ones.

Obviously, the graph that I collected is fully connected because of the method of collection, but since the network is so big I assume it got all linked towns or at least most of them.

You can look at the code and the data here, I appreciate input or further work.