Note that tuples are immutable in python. I usually use tuples as default values for collections: def f(x=()): x = list(x) ... def g(y=(())) y = dict(y

Note that tuples are immutable in python. I usually use tuples as default values for collections: def f(x=()): x = list(x) ... def g(y=(())) y = dict(y) ... f() is the pattern for lists, g() is for dicts. Note that you can pass in regular lists to f() and regular dicts to g().