collect_list
Collects the values from a column into a list, maintaining duplicates, and returns this list of objects. The function is non-deterministic as the order of collected results depends on the order of the rows, which possibly becomes non-deterministic after shuffle operations.
Syntax
Python
from pyspark.sql import functions as sf
sf.collect_list(col)
Parameters
Parameter | Type | Description |
|---|---|---|
|
| The target column on which the function is computed. |
Returns
pyspark.sql.Column: A new Column object representing a list of collected values, with duplicate values included.
Examples
Example 1: Collect values from a DataFrame and sort the result in ascending order
Python
from pyspark.sql import functions as sf
df = spark.createDataFrame([(1,), (2,), (2,)], ('value',))
df.select(sf.sort_array(sf.collect_list('value')).alias('sorted_list')).show()
Output
+-----------+
|sorted_list|
+-----------+
| [1, 2, 2]|
+-----------+
Example 2: Collect values from a DataFrame and sort the result in descending order
Python
from pyspark.sql import functions as sf
df = spark.createDataFrame([(2,), (5,), (5,)], ('age',))
df.select(sf.sort_array(sf.collect_list('age'), asc=False).alias('sorted_list')).show()
Output
+-----------+
|sorted_list|
+-----------+
| [5, 5, 2]|
+-----------+
Example 3: Collect values from a DataFrame with multiple columns and sort the result
Python
from pyspark.sql import functions as sf
df = spark.createDataFrame([(1, "John"), (2, "John"), (3, "Ana")], ("id", "name"))
df = df.groupBy("name").agg(sf.sort_array(sf.collect_list('id')).alias('sorted_list'))
df.orderBy(sf.desc("name")).show()
Output
+----+-----------+
|name|sorted_list|
+----+-----------+
|John| [1, 2]|
| Ana| [3]|
+----+-----------+