CODEWITHSUNDEEP
pythonlistfor-loop
Pithit
Pithit

Reputation: 471

creating a list of list for loop

This my code:

num= [2,10]

def calculo(lista):
    lista2 = []    
    for i in lista:
        for j in range(1, i + 1):
            if i % j == 0:
                lista2.append(j)
    return lista2

print(calculo(num))

Which produces: [1, 2, 1, 2, 5, 10]. However, I need the following result:

[[1, 2], [1, 2, 5, 10]]

In addition, I would like to know your approach through list comprehension.

Upvotes: 1

Views: 58

Answers (5)

Jonas Pirner
Jonas Pirner

Reputation: 152

if you want to use list comprehension

[[x for x in range(1, n+1) if n%x==0] for n in num]

Upvotes: 2

Zaraki Kenpachi
Zaraki Kenpachi

Reputation: 5730

num = [2,10]

def calculo(lista):
    result = [[j for j in range(1, i + 1) if i % j == 0] for i in lista]
    return result

print(calculo(num))

Output:

[[1, 2], [1, 2, 5, 10]]

Upvotes: 1

Mad Physicist
Mad Physicist

Reputation: 114310

You need to make the nested lists before the nested loop, just like you make the outer list before the outer loop:

num = [2,10]

def calculo(lista):
    lista2 = []    
    for i in lista:
        lista3 = []
        for j in range(1, i + 1):
            if i % j == 0:
                lista3.append(j)
        if lista3:
            lista2.append(lista3)
    return lista2

print(calculo(num))

Any time you have a sufficiently simple loop that appends items to a list, you can turn it into a list comprehension. For example, the inner loop becomes:

lista3 = [j for j in range(1, i + 1) if i % j == 0]

Now you can write the entire function as:

def calculo(lista):
    return [[j for j in range(1, i + 1) if i % j == 0] for i in lista]

Upvotes: 1

mousetail
mousetail

Reputation: 8010

You will need to create a new list for every iteration of the loop:

outer_list = []
for i in lista:
    inner_list = []
    for j in range(...):
        if ...:
            inner_list.append(...)
    outer_list.append(inner_list)
return outer_list

Upvotes: 2

miszcz2137
miszcz2137

Reputation: 914

This will foreach i loop append new list and then append new values to the last list

num= [2,10]

def calculo(lista):
    lista2 = []    
    for i in lista:
        lista2.append([])
        for j in range(1, i + 1):
            if i % j == 0:
                lista2[-1].append(j)
    return lista2

print(calculo(num))

Also in short form:

num= [2,10]

def calculo(lista):
    lista2 = [[j for j in range(1, i+1) if i % j == 0] for i in lista]
    return lista2

print(calculo(num))

Upvotes: 2

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