sum of nested list in Python

Question

I try to sum a list of nested elements

e.g, numbers=[1,3,5,6,[7,8]] should produce sum=30

I wrote the following code :

Answer 1

def nnl(nl): # non nested list function

    nn = []

    for x in nl:
        if type(x) == type(5):
            nn.append(x)

        if type(x) == type([]):
            n = nnl(x)

        for y in n:
            nn.append(y)

     return sum(nn)


 print(nnl([[9, 4, 5], [3, 8,[5]], 6])) # output:[9,4,5,3,8,5,6]

 a = sum(nnl([[9, 4, 5], [3, 8,[5]], 6]))
 print (a) # output: 40