将嵌套列表转换为元组

Question

How can I take a nested List and group it into a tuple of three without importing any module. Please show the expanded for loops so I can understand it better. For example, I want this nested List. Note this will always multiples of 3 sub lists so there is not a index error. Thankyou.

[[1], [2], [3], [4], [5], [6], [7], [8], [9]] # Given

[(1, 2, 3), (4, 5, 6), (7, 8, 9)] # Result Wanted

Answer 1

No need for indexes. You can use next() on an iterator even inside a for loop:

xss = [[1], [2], [3], [4], [5], [6], [7], [8], [9]]
it = iter(xss)
answer = []
for x, in it:
    answer.append((x, next(it)[0], next(it)[0]))

Answer 2

You can slice with a step size of 3 and zip to make the triples, do a nested unpacking in the for loop, and rebuild the triples without the wrapping lists.

xss = [[1], [2], [3], [4], [5], [6], [7], [8], [9]]
it = zip(xss[::3], xss[1::3], xss[2::3])
answer = []
for [x], [y], [z] in it:
    answer.append((x, y, z))

Answer 3

given = [[1], [2], [3], [4], [5], [6], [7], [8], [9]]  # because this is a list within a list

output = []

for i in range(0, len(given),3): # step size 3 indicated
    temp = (given[i][0], given[i+1][0], given[i+2][0]) # therefore you need the "[0]" behind each given[i]
    output.append(temp)
print (output)