在PySpark中，我需要将数据帧中的列(映射列表)转换为字符串

from pyspark.sql import SparkSession
from pyspark.sql.functions import concat_ws

# 创建SparkSession
spark = SparkSession.builder.getOrCreate()

# 创建示例数据帧
data = [("John", "Doe", 25), ("Jane", "Smith", 30), ("Bob", "Johnson", 35)]
df = spark.createDataFrame(data, ["first_name", "last_name", "age"])

# 将first_name和last_name列转换为字符串，并使用空格作为分隔符
df_with_string = df.withColumn("full_name", concat_ws(" ", df.first_name, df.last_name))

# 显示转换后的数据帧
df_with_string.show()

+----------+---------+---+-------------+
|first_name|last_name|age|    full_name|
+----------+---------+---+-------------+
|      John|      Doe| 25|    John Doe|
|      Jane|    Smith| 30|  Jane Smith|
|       Bob|  Johnson| 35|Bob Johnson|
+----------+---------+---+-------------+