PySpark Groupby Explained with Example

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  • Post category:PySpark
  • Post last modified:July 22, 2022

Similar to SQL GROUP BY clause, PySpark groupBy() function is used to collect the identical data into groups on DataFrame and perform count, sum, avg, min, max 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

1. GroupBy() Syntax & Usage

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() – Use groupBy() count() to return the number 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 groupBy() 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.

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, and total salary for each group using min(), max(), and sum() aggregate functions respectively.


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|
+-------------+----------+-----+------+---+-----+

2. PySpark groupBy 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() 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 employees in each department using.


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") 

3. Using 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 two or more columns for other aggregate functions, please refer to the below example.

4. Running more aggregates at a time

Using agg() aggregate function we can calculate many aggregations at a time on a single statement using SQL 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"


from pyspark.sql.functions import sum,avg,max
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    |
+----------+----------+-----------------+---------+---------+

5. 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.


from pyspark.sql.functions import sum,avg,max
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    |
+----------+----------+-----------------+---------+---------+

6. 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.

7. Conclusion

In this tutorial, you have learned how to use groupBy() functions on PySpark DataFrame and also learned how to run these on multiple columns and finally filter 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 !!

NNK

SparkByExamples.com is a Big Data and Spark examples community page, all examples are simple and easy to understand and well tested in our development environment Read more ..

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This Post Has 4 Comments

  1. Anonymous

    It was very straightforward. Thank you very much.

  2. Sr. Persona

    Thanks, very useful

  3. Sneha

    This is really great. I am learning pyspark in databricks and though there were a few syntax changes, the tutorial made me understand the concept properly.

    1. NNK

      Thanks, Sneha for your comments, and glad you like the articles. If you find any syntax changes in Databricks please do comment, others might get benefit from your findings.

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