PySpark - Parse a Column of JSON Strings

Introduction

Parsing JSON strings with PySpark is an essential task when working with large datasets in JSON format. By transforming JSON data into a structured format, you can enable efficient processing and analysis. PySpark provides a powerful way to parse these JSON strings and extract their contents into separate columns, making your data more structured and easier to work with. In this tutorial, we’ll go through the steps to parse JSON strings stored in a column and store their fields in separate columns in a PySpark DataFrame.

Import Libraries

First, import the following Python modules:

from pyspark.sql import SparkSession
from pyspark.sql.functions import col, from_json
from pyspark.sql.types import StructType, StructField, StringType, IntegerType

Create SparkSession

Before working with PySpark, a SparkSession must be created. The SparkSession serves as the entry point to all Spark functionalities. To create a basic SparkSession programmatically, use the following command:

spark = SparkSession \
    .builder \
    .appName("Python PySpark Example") \
    .getOrCreate()

Create PySpark DataFrame

Let's create an example PySpark DataFrame based on a list. To do this, use the createDataFrame() method of PySpark.

column_names = ["id", "information"]
data = [
    (0, '{"language":"Python","framework":"Django","users":20000}'),
    (1, '{"language":"Python","framework":"FastAPI","users":9000}'),
    (2, '{"language":"Java","framework":"Spring","users":7000}'),
    (3, '{"language":"JavaScript","framework":"ReactJS","users":5000}')
]
df = spark.createDataFrame(data, column_names)
df.show()

Output:

+---+--------------------+
| id|         information|
+---+--------------------+
|  0|{"language":"Pyth...|
|  1|{"language":"Pyth...|
|  2|{"language":"Java...|
|  3|{"language":"Java...|
+---+--------------------+

Parse JSON Strings

To parse the JSON strings in the information column and extract specific fields, use the from_json() function of PySpark. You’ll also need to define a schema for the JSON structure.