Python was heavily based on ABC, a language which targeted new programers and made syntax choices based on user testing: http://python-history.blogspot.ca/2009/02/early-language-design-and-development.html It says a lot about our understanding of our field that new languages generally do not formally test their syntaxes (and other "mental model" features) for usability.
But there is some weird stuff in Python syntax. Like, why do you create a dict with {} but access it with []? It always felt to me like an organic language, not one that was planned with consistency in mind (which is fine, of course).
Declaration doesn't reflect usage, it's not a helpful principle in general. You create tuples with () but access them with [], and the fact that [a, b, c] is a list has very little to do with the fact that you use [] to index into it. The {} syntax for dictionary literals is reasonably common; Ruby's looks fairly similar, and Javascript uses almost exactly the same syntax, which many people will be familiar with thanks to JSON. Are there any other popular syntices for dict literals?