检查所有元素是否都是唯一的不可用列表

Question

New to Python here. I've figured out that it's rather trivial to check if a list has all unique elements using

  if len(lst) > len(set(lst))

But how would I deal with a case like this?

all_different([[],[],[],[]]) #False

I can't use the set() function in this example. I understand how I might do this (rather inefficiently) with nested for loops in Java. But not sure how I could implement this in Python.

Answer 1

You can't hash lists as they're mutable, but you can convert them to tuples, and hash them instead. Like so: set(tuple(elem) for elem in lst)

Your comparison would then become:

myset = set(tuple(elem) for elem in lst)
if len(lst) > len(myset)