如何在Spark Structured Streaming中将多个列(仍未填充)添加到DataFrame

from pyspark.sql import SparkSession
from pyspark.sql.functions import lit

spark = SparkSession.builder.getOrCreate()

# 创建一个空的DataFrame
df = spark.createDataFrame([], schema="col1: string, col2: int, col3: double")

# 定义要添加的列
new_cols = [("col4", lit("value1")), ("col5", lit(10)), ("col6", lit(3.14))]

# 使用withColumn函数添加列
for col_name, col_expr in new_cols:
    df = df.withColumn(col_name, col_expr)

# 显示DataFrame的内容
df.show()