Extend the list to another list

Question

Well I have two lists, list1 and Lista2:

lista1 = [['carlos','10','cenouras','carro','agora'],['duarte','34','couves','bus','agora']] 

lista2 = [['11:30', '12:00'],['13:00', '13:30']]

What I want is to create a new list with the first 2 elements of each list inside the list1, getting: listaNova = [['carlos', '10'], ['duarte', '34']]

Next, to each list inside the listNew I want to add a list of Lista2, getting:

listaNova = [['carlos', '10', '11:30', '12:00'], ['duarte', '34', '13:00', '13:30']]

Finally I want to add the last element of the list1:

listaNova = [['carlos', '10', '11:30', '12:00','agora'], ['duarte', '34', '13:00', '13:30','agora']]

What I got is this:

listaNova =[]

for i in lista1:
   nomes = i[:2]
   listaNova.append(nomes)

But now I don’t know how to extend the rest..

Answer 1

You can correlate list elements lista1 and lista2 through function zip. Also, you can concatenate lists using the operator +. So if you create a new list - using list comprehensions - in which each element is e1[:2] + e2 + e1[-1:] you get what you want:

>>> lista1 = [['carlos','10','cenouras','carro','agora'],['duarte','34','couves','bus','agora']]

>>> lista2 = [['11:30', '12:00'],['13:00', '13:30']]

>>> listaNova = [e1[:2] + e2 + e1[-1:] for e1, e2 in zip(lista1, lista2)]

>>> listaNova
[['carlos', '10', '11:30', '12:00', 'agora'], ['duarte', '34', '13:00', '13:30', 'agora']]

(Note that I used e1[-1:] instead of simply e1[-1] because I want a list with an element, and not only the element)

If you want to do "in full" (i.e. using loops, append and extend), would look like this:

listaNova = []
for e1, e2 in zip(lista1, lista2):
    item = []
    listaNova.append(item) # append acrescenta um item na lista

    item.extend(e1[:2]) # extend acrescenta os itens do argumento na lista
    item.extend(e2)
    item.append(e1[-1]) # como é um único elemento, pode usar append

Finally, if you want to avoid the zip, can make a normal loop over the list contents (beware, make sure the lists are equal in size):

listaNova = []
for i in range(len(lista1)): # i vai de 0 a "tamanho da lista" - 1
    item = []
    listaNova.append(item)

    e1 = lista1[i]
    e2 = lista2[i]

    item.extend(e1[:2])
    item.extend(e2)
    item.append(e1[-1])

But note how the code gets extended, while the first method does the same thing using a single line of code... As you master these concepts (mainly list comprehension, one of the most powerful features of language) get used to using them in place of more verbose constructions, when appropriate.