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spark revision

 spark session 

First import Spark session from pyspark 

Define a Spark session 

spark = sparksession.bulider.appname("name").getorcreate()

spark session methods -->read, write, createDataframe, table, sql

Read the functions 


df1= spark.read.options().csv(file name )

                         .json(file name)

                         .text(file name)


options () --> multiline () --> df_multiline_json = spark.read.option("multiline", "true").json("multiline_json.json")

               delimiter --> df_pipe_delimited = spark.read.option("delimiter", "|").csv("file_without_header.csv")

               Header --> df_no_header = spark.read.csv("file_with_header.csv") # Default header=false

                          df_header = spark.read.option("header", "true").csv("file_with_header.csv")

               schema --> if there is no header, we need to construct the schema by structtype 

4. schema Option

print("\n--- schema Option ---")

custom_schema = StructType([

    StructField("person_id", IntegerType(), True),

    StructField("full_name", StringType(), True),

    StructField("age", IntegerType(), True)

])


df_with_schema = spark.read.option("header", "true").schema(custom_schema).csv("file_with_header.csv")

               inferschema --> df_infer_schema = spark.read.option("header", "true").option("inferSchema", "true").csv("file_with_header.csv")

df_infer_schema.show()

               format().load("file name") = if we need to expliity mention the file format and load the file 

df.createor ReplaceTempView("view name ")

spark.table("view name ")

we can change into 

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