If I know my_dict doesn't hold values that that are false-like, e.g. 0 or [], I use `or` to lazily alternate between options. This works because in python, `or` returns the first value that has a truthy value. In this case it would be
my_dict.get('existing_key') or foo()
This would also easily let you do multiple alternations (much more annoying with the ternary operator).
gp's approach works best when you know that the argument is a list or tuple (something which can be empty). Of course, due to python's lack of typing, you should only use that approach when the function is being used in well-understood contexts.
