User: #include <bits/stdc++.h>
#define int long long

using namespace std;

int32_t main() {
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    vector<int> a(2 * n), b(2 * n);

    for (int i = 0; i < 2 * n; i++)
      cin >> a[i];
    for (int i = 0; i < 2 * n; i++)
      cin >> b[i];

    vector<pair<int, int>> pairs;

    for (int i = 0; i < 2 * n; i++) {
      pairs.emplace_back(a[i], b[i]);
    }

    sort(pairs.begin(), pairs.end(),
         [](const pair<int, int> &x, const pair<int, int> &y) {
           return x.first + y.second < y.first + x.second;
         });

    int t = 0;

    for (int i = 0; i < n; i++)
      t += pairs[i].first;

    for (int i = n; i < 2 * n; i++)
      t += pairs[i].second;

    cout << t << endl;
  }
  return 0;
}
convert to python
Assistant: To convert the given C++ code to Python, we'll follow a similar logic and utilize Python's data structures, such as lists and tuples. We'll also use the `sorted()` function to sort the list of tuples. Here's the converted code:

```python
def main():
    import sys
    input = sys.stdin.read
    data = input().split()

    index = 0
    t = int(data[index])
    index += 1
    
    results = []
    for _ in range(t):
        n = int(data[index])
        index += 1
        
        a = []
        b = []
        
        for i in range(2 * n):
            a.append(int(data[index + i]))
        
        index += 2 * n
        
        for i in range(2 * n):
            b.append(int(data[index + i]))
        
        index += 2 * n
        
        pairs = [(a[i], b[i]) for i in range(2 * n)]
        
        pairs.sort(key=lambda x: x[0] + x[1])
        
        total = 0
        for i in range(n):
            total += pairs[i][0]  # First n elements, take a[i]
        for i in range(n, 2 * n):
            total += pairs[i][1]  # Last n elements, take b[i]
        
        results.append(total)
    
    for result in results:
        print(result)

if __name__ == "__main__":
    main()
```

### Explanation:
1. **Input Handling**: The Python version uses `sys.stdin.read` to read all input at once and splits it into individual elements. This approach is often used for competitive programming to handle large input sizes efficiently.

2. **Main Logic**: For each test case:
   - We extract the values of `n`, `a`, and `b` from the input.
   - Pairs of `(a[i], b[i])` are created and stored in a list.
   - These pairs are sorted based on the sum of elements in each tuple, similar to the custom comparator in the C++ code.
   - The sum `total` is calculated by taking the first element of the first `n` sorted pairs and the second element of the remaining pairs.

3. **Output**: The results for each test case are stored and then printed out in sequence.

This code assumes that all inputs are provided in one go, typical for competitive programming environments where input is often given as a whole rather than interactively. Adjust the input handling as needed for different environments.
User: remove comments
Assistant: Certainly! Here's the Python code without comments:

```python
def main():
    import sys
    input = sys.stdin.read
    data = input().split()

    index = 0
    t = int(data[index])
    index += 1
    
    results = []
    for _ in range(t):
        n = int(data[index])
        index += 1
        
        a = []
        b = []
        
        for i in range(2 * n):
            a.append(int(data[index + i]))
        
        index += 2 * n
        
        for i in range(2 * n):
            b.append(int(data[index + i]))
        
        index += 2 * n
        
        pairs = [(a[i], b[i]) for i in range(2 * n)]
        
        pairs.sort(key=lambda x: x[0] + x[1])
        
        total = 0
        for i in range(n):
            total += pairs[i][0]
        for i in range(n, 2 * n):
            total += pairs[i][1]
        
        results.append(total)
    
    for result in results:
        print(result)

if __name__ == "__main__":
    main()
```

This version is cleaner and more straightforward, focusing solely on the functionality without any added explanations.
User: dont use sys for input
Assistant: