Original code in JS:

// applying crossover
for (let i = cxpoint1; i < cxpoint2; i  ) {
  let temp1 = ind1[i]
  let temp2 = ind2[i]

  ind1[i]         = temp2
  ind1[p1[temp2]] = temp1

  ind2[i]         = temp1
  ind2[p2[temp1]] = temp2

  return [ind1, ind2]

New to JS and wondering what is happening on this line:

ind1[p1[temp2]] = temp1

Trying to understand so I can make an equivalent function in Python.

I understand the assignment, however obviously in Python you cannot use double brackets as shown on the line above. If someone could tell me the concept, I should be able to apply it to my situation.

Thanks in advance.

CodePudding user response：

To fully understand the code one would need to know how the arrays p1 and p2 look like, but I assume they are integer-arrays. You select an integer from that array in the inner statement that then is the index for the outer statement.

It works exactly the same in python:

ind1 = [1, 2, 3, 4, 5]
p1 = [3, 1, 2]
print(ind1[p1[0]])
# -> 4

In this example the inner statement resolves to 3 (first element in the p1-list) and the outer statement then resolves to 4 (fourth element in the ind1-list.

CodePudding user response：

There's nothing magical going on here.

ind1[p1[temp2]]

p1[temp2] resolves to some value, let's call it a. So the expression then becomes ind1[a].