访问列表元素的while循环问题

Question

• I want to append each element of [1,2] to [[1], [2], [3]] and as a consequence, the final array that I want is [[1,1], [1,2], [2,1], [2,2], [3,1], [3,2]]

  But my code has a mistake I couldn't recognize it yet, and the result of the python code below is [[1, 1, 2], [1, 1, 2], [2, 1, 2], [2, 1, 2], [3, 1, 2], [3, 1, 2]]

The python code:

tor=[]
arr=[1,2]
arz=[[1], [2], [3]]

each=0
while each<len(arz):
       
    eleman=arz[each]
    index=0
    while index < len(arr):
        k=arr[index]
        eleman=arz[each]
        eleman.append(k)
        tor.append(eleman)
        index = index+1
    
    each=each+1

Answer 1

it would be eleman=arz[each].copy() as lists are mutable so every time you change an element in the original list it will get reflected in the resultant array

Answer 2

In this example it would be more useful to use a for loop . You can use it to loop through both lists, and append in pairs.

arr = [1, 2]
arz = [[1], [2], [3]]
tor = []

for i in arz:
    for j in (arr):
        tor.append([i[0], j])

print(tor)

Answer 3

You can use Python list comprehension to achieve this in one line:

a1 = [1, 2]
a2 = [[1], [2], [3]]

result =  [[i[0], j] for i in a2 for j in a1]

print(result)

• For this kind of operations don't use While loop but the for loop. It is much cleaner and simpler to use with iterables.