[ulam2]

1. Python's list slicing and indexing is the perfect mix of simplicity, intuition and power. It is surprising how few languages have similar implementations.

2. Currying like in Haskell.

[skrtskrt]

Python list/set/dict comprehensions too

[hansvm]

And generator comprehensions -- it's especially nice that you can directly write things like `sum(x*x for x in g)` without needing an extra set of parentheses or allocating an intermediate collection.