PySpark: How to covert column with Ljava.lang.Object

问题

I created data frame in PySpark by reading data from HDFS like this:

df = spark.read.parquet('path/to/parquet')

I expect the data frame to have two column of strings:

+------------+------------------+
|my_column   |my_other_column   |
+------------+------------------+
|my_string_1 |my_other_string_1 |
|my_string_2 |my_other_string_2 |
|my_string_3 |my_other_string_3 |
|my_string_4 |my_other_string_4 |
|my_string_5 |my_other_string_5 |
|my_string_6 |my_other_string_6 |
|my_string_7 |my_other_string_7 |
|my_string_8 |my_other_string_8 |
+------------+------------------+

However, I get my_column column with some strings starting with [Ljava.lang.Object;, looking like this:

>> df.show(truncate=False)
+-----------------------------+------------------+
|my_column                    |my_other_column   |
+-----------------------------+------------------+
|[Ljava.lang.Object;@7abeeeb6 |my_other_string_1 |
|[Ljava.lang.Object;@5c1bbb1c |my_other_string_2 |
|[Ljava.lang.Object;@6be335ee |my_other_string_3 |
|[Ljava.lang.Object;@153bdb33 |my_other_string_4 |
|[Ljava.lang.Object;@1a23b57f |my_other_string_5 |
|[Ljava.lang.Object;@3a101a1a |my_other_string_6 |
|[Ljava.lang.Object;@33846636 |my_other_string_7 |
|[Ljava.lang.Object;@521a0a3d |my_other_string_8 |
+-----------------------------+------------------+

>> df.printSchema()
root
 |-- my_column: string (nullable = true)
 |-- my_other_column: string (nullable = true)

As you can see, my_other_column column is looking as expected. Is there any way, how to convert objects in my_column column to humanly readable strings?

回答1:

Jaroslav,

I tried with the following code, and have used a sample parquet file from here. I am able to get the desired output from the dataframe, can u please chk your code using the code snippet below and also sample file referred above to see if there's any other issue:

from pyspark.sql import SparkSession
spark = SparkSession.builder.appName("Read a Parquet file").getOrCreate()
df = spark.read.parquet('E:\\...\\..\\userdata1.parquet')
df.show(10)
df.printSchema()

Replace the path to your HDFS location.

Dataframe output for your reference:

来源：https://stackoverflow.com/questions/57748029/pyspark-how-to-covert-column-with-ljava-lang-object

标签

python

pyspark

HDFS

java.lang