`if key in dict` vs. `try/except` - which is more readable idiom?

Question

I have a question about idioms and readability, and there seems to be a clash of Python philosophies for this particular case:

I want to build dictionary A from dict

Answer 1

The rule in other languages is to reserve exceptions for exceptional conditions, i.e. errors that don't occur in regular use. Don't know how that rule applies to Python, as StopIteration shouldn't exist by that rule.