Forward Fill in Pyspark

pyspark_fill.py

import pyspark.sql.functions as F
from pyspark.sql import Window

df = spark.createDataFrame([
    ('d1',None),
    ('d2',10),
    ('d3',None),
    ('d4',30),
    ('d5',None),
    ('d6',None),
],('day','temperature'))

w_forward = Window.partitionBy().orderBy('day').rowsBetween(Window.unboundedPreceding,Window.currentRow)
w_backward = Window.partitionBy().orderBy('day').rowsBetween(Window.currentRow,Window.unboundedFollowing)
df.withColumn('fill_forward',F.last('temperature',ignorenulls=True).over(w_forward))\
  .withColumn('fill_both',F.first('fill_forward',ignorenulls=True).over(w_backward)).show()

'''
+---+-----------+------------+---------+
|day|temperature|fill_forward|fill_both|
+---+-----------+------------+---------+
| d1|       null|        null|       10|
| d2|         10|          10|       10|
| d3|       null|          10|       10|
| d4|         30|          30|       30|
| d5|       null|          30|       30|
| d6|       null|          30|       30|
+---+-----------+------------+---------+
'''

Thank you, it's very useful.
But before using it we need to import some libraries:-

import pyspark.sql.functions as F
from pyspark.sql import Window

Thank you