forward fill in pyspark

from pyspark.sql.functions import coalesce, last, first

df.withColumn('latitude_new', coalesce(last('latitude',True).over(w1), first('latitude',True).over(w2))) \
  .select('name','timestamplast', 'latitude','latitude_new') \
  .show()
+----+-------------------+---------+------------+
|name|      timestamplast| latitude|latitude_new|
+----+-------------------+---------+------------+
|   1|2019-08-01 00:00:00|     null|   51.819645|
|   1|2019-08-01 00:00:01|     null|   51.819645|
|   1|2019-08-01 00:00:02|51.819645|   51.819645|
|   1|2019-08-01 00:00:03| 51.81964|    51.81964|
|   1|2019-08-01 00:00:04|     null|    51.81964|
|   1|2019-08-01 00:00:05|     null|    51.81964|
|   1|2019-08-01 00:00:06|     null|    51.81964|
|   1|2019-08-01 00:00:07| 51.82385|    51.82385|
+----+-------------------+---------+------------+

cols = ['latitude', 'longitude']
df_new = df.select([ c for c in df.columns if c not in cols ] + [ coalesce(last(c,True).over(w1), first(c,True).over(w2)).alias(c) for c in cols ])