PySpark 면접 질문과 답변
Ques 16. How can you perform a union operation on two DataFrames in PySpark?
You can use the 'union' method to combine two DataFrames with the same schema.
Example:
result = df1.union(df2)
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Ques 17. Explain the purpose of the 'window' function in PySpark.
The 'window' function is used for defining windows over data based on partitioning and ordering, often used with aggregation functions.
Example:
from pyspark.sql.window import Window
from pyspark.sql.functions import sum
window_spec = Window.partitionBy('category').orderBy('value')
result = df.withColumn('sum_value', sum('value').over(window_spec))
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Ques 18. What is the purpose of the 'explode' function in PySpark?
The 'explode' function is used to transform a column with arrays or maps into multiple rows, duplicating the values of the other columns.
Example:
from pyspark.sql.functions import explode
exploded_df = df.select('ID', explode('items').alias('item'))
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Ques 19. Explain the concept of 'broadcast' variables in PySpark.
'Broadcast' variables are read-only variables cached on each node of a cluster to efficiently distribute large read-only data structures.
Example:
from pyspark.sql.functions import broadcast
result = df1.join(broadcast(df2), 'key')
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Ques 20. How can you handle missing or null values in a PySpark DataFrame?
You can use the 'na' functions like 'drop' or 'fill' to handle missing values in a PySpark DataFrame.
Example:
df.na.drop()
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