zip argument #1 must support iteration (did not understand this error)

Question

I have the following code.

  v1 = [1,2]
v2 = [2,1]

def vector_add(v, w):
    '''Soma entre dois vetores'''
    return [v_i + w_i for v_i, w_i in zip(v,w)]

def vector_subtract(v, w):
    '''Subtrai elementos correspondentes'''
    return [v_i - w_i for v_i, w_i in zip(v,w)]

print('Soma -> ', vector_add(v1, v2))
print('Subtração -> ', vector_subtract(v1, v2))

Which is working normally. However, I have one more in which the error appears.

def vector_sum(vectors):
    '''Soma de todos os elementos do vetor'''
    result = vectors[0] #Result recebe o primeiro valor do vetor
    for vector in vectors[1:]: #Depois passa por todos os outros
        result = vector_add(result, vector) #E adiciona ao resultado
    return result

vetorX = [5, 5, 5, 5, 20]
print('Soma de todos os elementos do vetor -> ', vector_sum(vetorX))

This returns me the following error:

--------------------------------------------------------------------------- Typeerror Traceback (Most recent call last) in 7 8 vetorX = [5, 5, 5, 5, 20] ----> 9 print('Sum of all elements of the vector -> ', vector_sum(vetorX))

in vector_sum(Vectors) 3 result = Vectors[0] #Result gets the first vector value 4 for vector in Vectors[1:]: #Then go through all the others ----> 5 result = vector_add(result, vector) #E adds to result 6 Return result 7

in vector_add(v, w) 4 def vector_add(v, w): 5 ''Sum between two vectors'' -----> 6 Return [v_i + w_i for v_i, w_i in zip(v,w)] 7 8 def vector_subtract(v, w):

Typeerror: zip argument #1 must support iteration

Why does this mistake happen?

Answer 1

According to the documentation, zip takes several iterable objects (such as lists or tuples, for example) as parameters.

In your case, you created vetorX = [5, 5, 5, 5, 20] and passed this list to vector_sum.

Within the function vector_sum, took the first element from the list (result = vectors[0]). At this point, result is equal to 5. In the first iteration of for, you pass this value (5) to vector_add, which in turn passes it to zip.

Only the number 5 is not an eternal object, and that is what is being said in the error message ("zip argument #1 must support iteration").

---

It is unclear what you want the result to be. If you want to add up all the numbers of vetorX, for example, just do sum(vetorX).

If the goal is to generate a list in which each element is added with the first number of vetorX (except for the first element itself), so it looks like this:

vetorX = [5, 5, 5, 5, 20]
primeiro = vetorX[0]
result = [i + primeiro for i in vetorX[1:]]
print(result) # [10, 10, 10, 25]

Anyway, whatever you’re trying to do, zip is useful to browse two or more lists simultaneously. If you only have one list (in case, vetorX), there’s nothing to use zip.