计算列表内列表的长度

my_list = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
length = len(my_list)
print(length)

List<List<Integer>> myList = new ArrayList<>();
myList.add(Arrays.asList(1, 2, 3));
myList.add(Arrays.asList(4, 5, 6));
myList.add(Arrays.asList(7, 8, 9));
int length = myList.size();
System.out.println(length);

let myList = [[1, 2, 3], [4, 5, 6], [7, 8, 9]];
let length = myList.length;
console.log(length);

#include <iostream>
#include <vector>
using namespace std;

int main() {
    vector<vector<int>> myList = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
    int length = myList.size();
    cout << length << endl;
    return 0;
}