PySpark “ImportError: No module named py4j.java_gateway” Error

Problem: When I was running PySpark commands after successful installation of PySpark on Linux, I got an error “<strong>ImportError: No module named py4j.java_gateway</strong>“, I had spent some time and understand what is Py4J module and resolve the issue. I would like to share it here.


ImportError: No module named py4j.java_gateway

Solution: Resolve ImportError: No module named py4j.java_gateway

In order to resolve “<strong>ImportError: No module named py4j.java_gateway</strong>” Error, first understand what is the py4j module. Spark basically written in Scala and later due to its industry adaptation, it’s API PySpark released for Python using Py4J.

Py4J is a Java library that is integrated within PySpark and allows python to dynamically interface with JVM objects. so Py4J is a mandatory module to run the PySpark application and it is located at $SPARK_HOME/python/lib/py4j-*-src.zip directory.

After Spark installation, you need to set Py4j module to PYTHONPATH environment variable in order to run the PySpark application. Not setting this module to env, you get ImportError: No module named py4j.java_gateway error.


export SPARK_HOME=/Users/prabha/apps/spark-3.0.0-bin-hadoop2.7
export PYTHONPATH=$SPARK_HOME/python:$SPARK_HOME/python/build:$SPARK_HOME/python/lib/py4j-0.10.9-src.zip:$PYTHONPATH

Put these on .bashrc file and re-load the file by using source ~/.bashrc

Based on the PySpark version you are using, the py4j module version also changes, in order to set this version right from the path use below.


export PYTHONPATH=${SPARK_HOME}/python/:$(echo ${SPARK_HOME}/python/lib/py4j-*-src.zip):${PYTHONPATH}

To know the path of the PySpark location use pip show command.


pip show pyspark

On Windows, use the below environment variables to resolve ImportError: No module named py4j.java_gateway error.


set SPARK_HOME=C:\apps\opt\spark-3.0.0-bin-hadoop2.7
set HADOOP_HOME=%SPARK_HOME%
set PYTHONPATH=%SPARK_HOME%/python;%SPARK_HOME%/python/lib/py4j-0.10.9-src.zip;%PYTHONPATH%

Conclusion

To resolve ImportError: No module named py4j.java_gateway error in PySpark, set the py4j module from ${SPARK_HOME}/python/lib directory to PYTHONPATH environment variable.

Happy Learning !!

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