Difference between dict.clear() and assigning {} in Python

Question

In python, is there a difference between calling clear() and assigning {} to a dictionary? If yes, what is it? Example:

d = {\"stuff\":\"         


        

Answer 1

In addition, sometimes the dict instance might be a subclass of dict (defaultdict for example). In that case, using clear is preferred, as we don't have to remember the exact type of the dict, and also avoid duplicate code (coupling the clearing line with the initialization line).

x = defaultdict(list)
x[1].append(2)
...
x.clear() # instead of the longer x = defaultdict(list)

Answer 2

If you have another variable also referring to the same dictionary, there is a big difference:

>>> d = {"stuff": "things"}
>>> d2 = d
>>> d = {}
>>> d2
{'stuff': 'things'}
>>> d = {"stuff": "things"}
>>> d2 = d
>>> d.clear()
>>> d2
{}

This is because assigning d = {} creates a new, empty dictionary and assigns it to the d variable. This leaves d2 pointing at the old dictionary with items still in it. However, d.clear() clears the same dictionary that d and d2 both point at.