This community-built FAQ covers the “Motivate our Lazy Friends with Actions” exercise from the lesson “RDDs with PySpark”.
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This exercise can be found in the following Codecademy content:
[Beta] Introduction to Big Data with PySpark
FAQs on the exercise Motivate our Lazy Friends with Actions
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I guess the answer for the first question under ‘Actions’ should be:
Running the cell gives the desired output. However, this is not accepted by the program.
Your code did not produce an output. Make sure your code has been saved in the designated code cell and that it produces an output when run.
i ve got the same problem, tried everything nothing worked
Ok so i figured it out, every time you execute any cell you have to save the notebook by clicking ‘Save and Checkpoint’ in the upper left
How can you apply logic that has to be sequential when spark evaluates the code at a later point in time?
The lesson states:
rdd = spark.SparkContent.parallelize([1,2,3,4,5])rdd.map(lambda x: x+1).filter(lambda x: x>3)
Instead of following the order that we called the transformations, Spark might load the values greater than 3 into memory first and perform the map function last. This swap will save memory and time because Spark loaded fewer data points and mapped the lambda to fewer elements.
What if I my logic requires that x + 1 takes places so that x = 2 is not filtered out in the next step? Is there any way to ensure that the lazy execution takes this type of sequence into consideration?
Wrong definition in RDDS WITH PYSPARK 4/8
The key thing about actions is that, like transformations, they take an RDD as input, but they will always output a value instead of a new RDD.
however the syntax for this is stated as:
rdd.reduce(lambda x,y: x+y)
Therefore it is a method on the object and not a function which take the object (RDD) as an input.