On Thu, Jan 20, 2011 at 11:47 AM, Tim Delaney <email@example.com>
['b':1] would then be ambiguous (appears to be a slice of a list). More obvious in the case of [1:2] ...
We use parenthesis for tuples and avoid the ambiguity by writing (1,).
In the same way, we could require your examples to be written ['b':1,] and [1:2,]