CODEWITHSUNDEEP
pythonapache-sparkapache-spark-sqlpyspark
user0204
user0204

Reputation: 261

Split string column based on delimiter and create columns for each value in Pyspark

I have 1000s of files with data in the below format:

a|b|c|clm4=1|clm5=3
a|b|c|clm4=9|clm6=60|clm7=23

And I want to read it and convert it to a dataframe as below:

clm1|clm2|clm3|clm4|clm5|clm6|clm7
a|b|c|1|3|null|null
a|b|c|9|null|60|23

I have tried the below method:

files = [f for f in glob.glob(pathToFile + "/**/*.txt.gz", recursive=True)]
df = spark.read.load(files, format='csv', sep = '|', header=None)

But it is giving me below result:

clm1, clm2, clm3, clm4, clm5
a, b, c, 1, 3
a, b, c, 9, null

Upvotes: 2

Views: 777

Answers (1)

blackbishop
blackbishop

Reputation: 32640

For Spark 2.4+, you can read the files as a single column then split it by |. You'll get an array column that you could transform using higher-order functions:

df.show(truncate=False)

+----------------------------+
|clm                         |
+----------------------------+
|a|b|c|clm4=1|clm5=3         |
|a|b|c|clm4=9|clm6=60|clm7=23|
+----------------------------+

We use transform function to convert the array of string that we get from splitting the clm column into an array of structs. Each struct contains column name if present (check if a string contains =) or name it clm + (i+1) where i is its position. 

transform_expr = """
transform(split(clm, '[|]'), (x, i) -> 
                   struct(
                         IF(x like '%=%', substring_index(x, '=', 1), concat('clm', i+1)), 
                         substring_index(x, '=', -1)
                         )
        )
"""

Now use map_from_entries to convert the array to map. And finally, explode the map and pivot to get your columns

df.select("clm", 
          explode(map_from_entries(expr(transform_expr))).alias("col_name", "col_value")
         ) \
  .groupby("clm").pivot('col_name').agg(first('col_value')) \
  .drop("clm") \
  .show(truncate=False)

Gives:

+----+----+----+----+----+----+----+
|clm1|clm2|clm3|clm4|clm5|clm6|clm7|
+----+----+----+----+----+----+----+
|a   |b   |c   |9   |null|60  |23  |
|a   |b   |c   |1   |3   |null|null|
+----+----+----+----+----+----+----+

Upvotes: 1

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