The alternative here (which would make your example work) is that dictionary lookups return some falsy sentinel value when the key does not exist, just like in javascript. In javascript, this has made a lot of people very angry and been widely regarded as a bad move.

Those values tend to propagate out and make a mess, sneaking into your stored data or causing errors in unexpected places -- fixing this feels like one of the main advantages of using things like typescript, and it's just not an issue in python.

It's not a problem, because the alternative is way worse. It's just a different language design than the one you're used to.

You could argue about whether or not truthiness makes sense as a concept (personally I think not), but the way it's defined in python is quite coherent and useful in practice.