如何合并DataSet中的两列？

import pandas as pd

# 创建一个 DataSet
data = {'Column1': [1, 2, 3], 'Column2': ['a', 'b', 'c']}
df = pd.DataFrame(data)

# 合并两列
df['MergedColumn'] = df['Column1'].astype(str) + df['Column2']

const data = [
  { column1: 1, column2: 'a' },
  { column1: 2, column2: 'b' },
  { column1: 3, column2: 'c' },
];

const mergedData = data.map(item => {
  return { ...item, mergedColumn: `${item.column1}${item.column2}` };
});

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class Main {
    public static void main(String[] args) {
        List<Map<String, Object>> data = new ArrayList<>();
        data.add(Map.of("column1", 1, "column2", "a"));
        data.add(Map.of("column1", 2, "column2", "b"));
        data.add(Map.of("column1", 3, "column2", "c"));

        List<Map<String, Object>> mergedData = data.stream()
                .map(item -> {
                    Map<String, Object> newItem = new HashMap<>(item);
                    newItem.put("mergedColumn", item.get("column1") + item.get("column2"));
                    return newItem;
                })
                .collect(Collectors.toList());
    }
}