PySpark Groupby Explained with Example

Similar to SQL GROUP BY clause, PySpark groupBy() function is used to collect the identical data into groups on DataFrame and perform aggregate functions on the grouped data. In this article, I will explain several groupBy() examples using PySpark (Spark with Python).

Related: How to group and aggregate data using Spark and Scala

Syntax:

groupBy(col1 : scala.Predef.String, cols : scala.Predef.String*) :
      org.apache.spark.sql.RelationalGroupedDataset

When we perform groupBy() on PySpark Dataframe, it returns GroupedData object which contains below aggregate functions.

count() - Returns the count of rows for each group.

mean() - Returns the mean of values for each group.

max() - Returns the maximum of values for each group.

min() - Returns the minimum of values for each group.

sum() - Returns the total for values for each group.

avg() - Returns the average for values for each group.

agg() - Using agg() function, we can calculate more than one aggregate at a time.

pivot() - This function is used to Pivot the DataFrame which I will not be covered in this article as I already have a dedicated article for Pivot & Unpivot DataFrame.

Preparing Data & creating DataFrame

Before we start, let’s create the DataFrame from a sequence of the data to work with. This DataFrame contains columns “employee_name”, “department”, “state“, “salary”, “age” and “bonus” columns.

We will use this PySpark DataFrame to run groupBy() on “department” columns and calculate aggregates like minimum, maximum, average, total salary for each group using min(), max() and sum() aggregate functions respectively. and finally, we will also see how to do group and aggregate on multiple columns.

simpleData = [("James","Sales","NY",90000,34,10000),
    ("Michael","Sales","NY",86000,56,20000),
    ("Robert","Sales","CA",81000,30,23000),
    ("Maria","Finance","CA",90000,24,23000),
    ("Raman","Finance","CA",99000,40,24000),
    ("Scott","Finance","NY",83000,36,19000),
    ("Jen","Finance","NY",79000,53,15000),
    ("Jeff","Marketing","CA",80000,25,18000),
    ("Kumar","Marketing","NY",91000,50,21000)
  ]

schema = ["employee_name","department","state","salary","age","bonus"]
df = spark.createDataFrame(data=simpleData, schema = schema)
df.printSchema()
df.show(truncate=False)

Yields below output.

+-------------+----------+-----+------+---+-----+
|employee_name|department|state|salary|age|bonus|
+-------------+----------+-----+------+---+-----+
|        James|     Sales|   NY| 90000| 34|10000|
|      Michael|     Sales|   NY| 86000| 56|20000|
|       Robert|     Sales|   CA| 81000| 30|23000|
|        Maria|   Finance|   CA| 90000| 24|23000|
|        Raman|   Finance|   CA| 99000| 40|24000|
|        Scott|   Finance|   NY| 83000| 36|19000|
|          Jen|   Finance|   NY| 79000| 53|15000|
|         Jeff| Marketing|   CA| 80000| 25|18000|
|        Kumar| Marketing|   NY| 91000| 50|21000|
+-------------+----------+-----+------+---+-----+

PySpark groupBy and aggregate on DataFrame columns

Let’s do the groupBy() on department column of DataFrame and then find the sum of salary for each department using sum() aggregate function.

df.groupBy("department").sum("salary").show(truncate=False)
+----------+-----------+
|department|sum(salary)|
+----------+-----------+
|Sales     |257000     |
|Finance   |351000     |
|Marketing |171000     |
+----------+-----------+

Similarly, we can calculate the number of employee in each department using count()

df.groupBy("department").count()

Calculate the minimum salary of each department using min()

df.groupBy("department").min("salary")

Calculate the maximin salary of each department using max()

df.groupBy("department").max("salary")

Calculate the average salary of each department using avg()

df.groupBy("department").avg( "salary")

Calculate the mean salary of each department using mean()

df.groupBy("department").mean( "salary") 

PySpark groupBy and aggregate on multiple columns

Similarly, we can also run groupBy and aggregate on two or more DataFrame columns, below example does group by on department,state and does sum() on salary and bonus columns.

//GroupBy on multiple columns
df.groupBy("department","state") \
    .sum("salary","bonus") \
    .show(false)

This yields the below output.

+----------+-----+-----------+----------+
|department|state|sum(salary)|sum(bonus)|
+----------+-----+-----------+----------+
|Finance   |NY   |162000     |34000     |
|Marketing |NY   |91000      |21000     |
|Sales     |CA   |81000      |23000     |
|Marketing |CA   |80000      |18000     |
|Finance   |CA   |189000     |47000     |
|Sales     |NY   |176000     |30000     |
+----------+-----+-----------+----------+

similarly, we can run group by and aggregate on tow or more columns for other aggregate functions, please refer below source code for example.

Running more aggregates at a time

Using agg() aggregate function we can calculate many aggregations at a time on a single statement using PySpark SQL aggregate functions sum(), avg(), min(), max() mean() e.t.c. In order to use these, we should import "from pyspark.sql.functions import sum,avg,max,min,mean,count"

df.groupBy("department") \
    .agg(sum("salary").alias("sum_salary"), \
         avg("salary").alias("avg_salary"), \
         sum("bonus").alias("sum_bonus"), \
         max("bonus").alias("max_bonus") \
     ) \
    .show(truncate=False)

This example does group on department column and calculates sum() and avg() of salary for each department and calculates sum() and max() of bonus for each department.

+----------+----------+-----------------+---------+---------+
|department|sum_salary|avg_salary       |sum_bonus|max_bonus|
+----------+----------+-----------------+---------+---------+
|Sales     |257000    |85666.66666666667|53000    |23000    |
|Finance   |351000    |87750.0          |81000    |24000    |
|Marketing |171000    |85500.0          |39000    |21000    |
+----------+----------+-----------------+---------+---------+

Using filter on aggregate data

Similar to SQL “HAVING” clause, On PySpark DataFrame we can use either where() or filter() function to filter the rows of aggregated data.

df.groupBy("department") \
    .agg(sum("salary").alias("sum_salary"), \
      avg("salary").alias("avg_salary"), \
      sum("bonus").alias("sum_bonus"), \
      max("bonus").alias("max_bonus")) \
    .where(col("sum_bonus") >= 50000) \
    .show(truncate=False)

This removes the sum of a bonus that has less than 50000 and yields below output.

+----------+----------+-----------------+---------+---------+
|department|sum_salary|avg_salary       |sum_bonus|max_bonus|
+----------+----------+-----------------+---------+---------+
|Sales     |257000    |85666.66666666667|53000    |23000    |
|Finance   |351000    |87750.0          |81000    |24000    |
+----------+----------+-----------------+---------+---------+

PySpark groupBy Example Source code

import pyspark
from pyspark.sql import SparkSession
from pyspark.sql.functions import col,sum,avg,max

spark = SparkSession.builder.appName('SparkByExamples.com').getOrCreate()

simpleData = [("James","Sales","NY",90000,34,10000),
    ("Michael","Sales","NY",86000,56,20000),
    ("Robert","Sales","CA",81000,30,23000),
    ("Maria","Finance","CA",90000,24,23000),
    ("Raman","Finance","CA",99000,40,24000),
    ("Scott","Finance","NY",83000,36,19000),
    ("Jen","Finance","NY",79000,53,15000),
    ("Jeff","Marketing","CA",80000,25,18000),
    ("Kumar","Marketing","NY",91000,50,21000)
  ]

schema = ["employee_name","department","state","salary","age","bonus"]
df = spark.createDataFrame(data=simpleData, schema = schema)
df.printSchema()
df.show(truncate=False)

df.groupBy("department").sum("salary").show(truncate=False)

df.groupBy("department").count().show(truncate=False)


df.groupBy("department","state") \
    .sum("salary","bonus") \
   .show(truncate=False)

df.groupBy("department") \
    .agg(sum("salary").alias("sum_salary"), \
         avg("salary").alias("avg_salary"), \
         sum("bonus").alias("sum_bonus"), \
         max("bonus").alias("max_bonus") \
     ) \
    .show(truncate=False)
    
df.groupBy("department") \
    .agg(sum("salary").alias("sum_salary"), \
      avg("salary").alias("avg_salary"), \
      sum("bonus").alias("sum_bonus"), \
      max("bonus").alias("max_bonus")) \
    .where(col("sum_bonus") >= 50000) \
    .show(truncate=False)

This example is also available at GitHub PySpark Examples project for reference.

Conclusion

In this tutorial, you have learned how to use groupBy() and aggregate functions on PySpark DataFrame and also learned how to run these on multiple columns and finally filtering data on the aggregated columns.

Thanks for reading. If you like it, please do share the article by following the below social links and any comments or suggestions are welcome in the comments sections! 

Happy Learning !!