Question

my code:

a=[1,2,3,4]
b=a[:2]
c=[]
c[b]='sss'#error

memoize function:

def memoize(func, cache, num_args):
    def wrapper(*args):
        mem_args = args[:num_args]#<------this
        if mem_args in cache:
            return cache[mem_args]
        result = func(*args)
        cache[mem_args] = result#<-----and this
        return result

Answer 1

In the memoize function, I’m assuming cache is a dict. Also, since a is a list, b will also be a list, and lists are not hashable. Use a tuple.

Try

a = (1, 2, 3, 4) # Parens, not brackets
b = a[:2]
c = {} # Curly braces, not brackets
c[b] = 'sss'