我想从pyspark数据帧中获取每列的最大长度。
以下是示例数据帧：
from pyspark.sql.types import StructType,StructField, StringType, IntegerType
data2 = [("James","","Smith","36636","M",3000),
("Michael","Rose","","40288","M",4000),
("Robert","","Williams","42114","M",4000),
("Maria","Anne","Jones","39192","F",4000),
("Jen","Mary","Brown","","F",-1)
]
schema = StructType([ \
StructField("firstname",StringType(),True), \
StructField("middlename",StringType(),True), \
StructField("lastname",StringType(),True), \
StructField("id", StringType(), True), \
StructField("gender", StringType(), True), \
StructField("salary", IntegerType(), True) \
])
df = spark.createDataFrame(data=data2,schema=schema)
我尝试实现Scala中提供的解决方案，但无法转换它。
这会管用的
from pyspark.sql.functions import col, length, max
df=df.select([max(length(col(name))) for name in df.schema.names])
结果
编辑：供参考：转换为行（如这里所问，也在那里更新-数据框中每列的pyspark最大字符串长度）
df = df.select([max(length(col(name))).alias(name) for name in df.schema.names])
row=df.first().asDict()
df2 = spark.createDataFrame([Row(col=name, length=row[name]) for name in df.schema.names], ['col', 'length'])
输出：
