Idea is good by the tool is not good enough -- it only notices the population centres that author has took a note of, this looks like unintentional confirmation bias.

See my reply to author with fixes.

I've added London, as per your transient request, which is now deleted. I also changed the comments to "select cities", as this code by no means represents a comprehensive analysis over all possible cities.

I just pasted my original code with properly indenting in here, so I thought to remove ugliness once I copied it pastebin.

Also I saw some small city in california 'Los something...' with population of 28k which didn't get caught by the first function that only lists 50 most populous cities so I wrote the second one that includes every town in US.