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PySpark Column | dropFields method

schedule Aug 12, 2023
Last updated
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PySpark
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PySpark Column's dropFields(~) method returns a new PySpark Column object with the specified nested fields removed.

Parameters

1. *fieldNames | string

The nested fields to remove.

Return Value

A PySpark Column.

Examples

Consider the following PySpark DataFrame with some nested Rows:

data = [
Row(name="Alex", age=20, friend=Row(name="Bob",age=30,height=150)),
Row(name="Cathy", age=40, friend=Row(name="Doge",age=40,height=180))
]
df = spark.createDataFrame(data)
df.show()
+-----+---+---------------+
| name|age| friend|
+-----+---+---------------+
| Alex| 20| {Bob, 30, 150}|
|Cathy| 40|{Doge, 40, 180}|
+-----+---+---------------+

The schema of this PySpark DataFrame is as follows:

root
|-- name: string (nullable = true)
|-- age: long (nullable = true)
|-- friend: struct (nullable = true)
| |-- name: string (nullable = true)
| |-- age: long (nullable = true)
| |-- height: long (nullable = true)

Dropping certain nested fields in PySpark Column

To remove the age and height fields under friend, use the dropFields(~) method:

updated_col = df["friend"].dropFields("age", "height")
df_new = df.withColumn("friend", updated_col)
df_new.show()
+-----+---+------+
| name|age|friend|
+-----+---+------+
| Alex| 20| {Bob}|
|Cathy| 40|{Doge}|
+-----+---+------+

Here, note the following:

  • we are using the withColumn(~) method to update the friend column with the new column returned by dropFields(~).

The schema of this updated PySpark DataFrame is as follows:

df_new.printSchema()
root
|-- name: string (nullable = true)
|-- age: long (nullable = true)
|-- friend: struct (nullable = true)
| |-- name: string (nullable = true)

Notice how the age and height fields are no longer present under friend.

NOTE

Even if the nested field you wish to delete does not exist, no error will be thrown:

updated_col = df["friend"].dropFields("ZZZZZZZZZ")
df_new = df.withColumn("friend", updated_col)
df_new.show()
+-----+---+---------------+
| name|age| friend|
+-----+---+---------------+
| Alex| 20| {Bob, 30, 150}|
|Cathy| 40|{Doge, 40, 180}|
+-----+---+---------------+

Here, the nested field "ZZZZZZZZZ" obviously does not exist but no error was thrown.

robocat
Published by Isshin Inada
Edited by 0 others
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