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

A quick recursion that uses a lambda to handle the nested lists:

rec = lambda x: sum(map(rec, x)) if isinstance(x, list) else x

rec, applied on a list, will return the sum (recursively), on a value, return the value.

result = rec(a)

Answer 2

This code also works.

def add_all(t):
    total = 0
    for i in t:
        if type(i) == list: # check whether i is list or not
            total = total + add_all(i)
        else:
            total += i
    return total

Answer 3

 def sum_nest_lst(lst):
         t=0
         for l in lst:
             if(type(l)==int):
                 t=t+l
             if(type(l)==list):
                 t=t+sum(l)
         print(t)

Answer 4

def nested_sum(lists):
total = 0
for lst in lists:
    s = sum(lst)
    total += s
return total

Answer 5

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

Answer 6

It is generally considered more pythonic to duck type, rather than explicit type checking. Something like this will take any iterable, not just lists:

def nested_sum(a) :
    total = 0
    for item in a :
        try:
            total += item
        except TypeError:
            total += nested_sum(item)
    return total