How to cast string to ArrayType of dictionary (JSON) in PySpark

Question

Trying to cast StringType to ArrayType of JSON for a dataframe generated form CSV.

Using pyspark on Spark2

The CSV file I am dealin

Answer 1

Use from_json with a schema that matches the actual data in attribute3 column to convert json to ArrayType:

Original data frame:

df.printSchema()
#root
# |-- date: string (nullable = true)
# |-- attribute2: string (nullable = true)
# |-- count: long (nullable = true)
# |-- attribute3: string (nullable = true)

from pyspark.sql.functions import from_json
from pyspark.sql.types import *

Create the schema:

schema = ArrayType(
    StructType([StructField("key", StringType()), 
                StructField("key2", IntegerType())]))

Use from_json:

df = df.withColumn("attribute3", from_json(df.attribute3, schema))

df.printSchema()
#root
# |-- date: string (nullable = true)
# |-- attribute2: string (nullable = true)
# |-- count: long (nullable = true)
# |-- attribute3: array (nullable = true)
# |    |-- element: struct (containsNull = true)
# |    |    |-- key: string (nullable = true)
# |    |    |-- key2: integer (nullable = true)

df.show(1, False)
#+----------+----------+-----+------------------------------------+
#|date      |attribute2|count|attribute3                          |
#+----------+----------+-----+------------------------------------+
#|2017-09-03|attribute1|2    |[[value, 2], [value, 2], [value, 2]]|
#+----------+----------+-----+------------------------------------+