我想在每个循环中选择不同的元素

Question

I want to choose different element of array in each loop. For example, in the code below array and loop counts are not equal to length of array. But I must choose some elements in the main loop and then I will append my choices to new array.

   e1=[1,2,3,4,5,6,7,8,9,10]
      c=0
      e2=[]
   while c<=3:
      c+=1
      for i in e1:
          e2.append(i)

    print(e2)

.

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

But I want to choose 1 in first loop, 2 in second loop and 3 in third loop. So new array must be [1, 2, 3]. But every element of array is generated automatically.

Answer 1

e1=[1,2,3,4,5,6,7,8,9,10]
e2=[]
c=0
while c<3:
    e2.append(e1[c])
    c+=1
print(e2)

output

[1,2,3]

Answer 2

In python, [] are called lists.

When you are writing for i in e1 , it iterates over every element in the list e1 , and then e2.append(i) appends every one of this i into the new list e2 . Effectively the statement while c<=3: makes sure you do this (append every item of e1 to e2 for three times) which is not what you want. @prashant's comment would be one way to do what you want. A more pythonic way would be, unless I am mistaken about what you want:

e1=[1,2,3,4,5,6,7,8,9,10]
c=0
e2=[]
for i in e1[:3]:
    e2.append(i)
print(e2)

Every item in a list can be accessed as list[item_index] ie e1[0] is 1 , e1[3] is 4 , etc. And lists can be 'sliced' as list[start_index:end_index+1] ie e1[0:3] gives [1,2,3] ie e1[0], e1[1], e1[2]