How to calculate cumulative sum over date range excluding weekends in PySpark 2.0?

This is an extension to an earlier question I raised here How to calculate difference between dates excluding weekends in PySpark 2.2.0. My spark dataframe looks like below and can be generated with the accompanying code:

df = spark.createDataFrame([(1, "John Doe", "2020-11-30",1),(2, "John Doe", "2020-11-27",2),(4, "John Doe", "2020-12-01",0),(5, "John Doe", "2020-10-02",1),
                          (6, "John Doe", "2020-12-03",1),(7, "John Doe", "2020-12-04",1)],
                            ("id", "name", "date","count"))

+---+--------+----------+-----+
| id|    name|      date|count|
+---+--------+----------+-----+
|  5|John Doe|2020-10-02|    1|
|  2|John Doe|2020-11-27|    2|
|  1|John Doe|2020-11-30|    1|
|  4|John Doe|2020-12-01|    0|
|  6|John Doe|2020-12-03|    1|
|  7|John Doe|2020-12-04|    1|
+---+--------+----------+-----+

I am trying to calculate cumulative sums over a period of 2,3,4,5 & 30 days. Below is a sample code for 2 days and the resulting table.

from pyspark.sql.types import IntegerType
from pyspark.sql.functions import udf
days = lambda i: i * 86400
windowval_2 = Window.partitionBy("name").orderBy(F.col("date").cast("timestamp").cast("long")).rangeBetween(days(-1), days(0))
windowval_3 = Window.partitionBy("name").orderBy(F.col("date").cast("timestamp").cast("long")).rangeBetween(days(-2), days(0))
windowval_4 = Window.partitionBy("name").orderBy(F.col("date").cast("timestamp").cast("long")).rangeBetween(days(-3), days(0))
df = df.withColumn("cum_sum_2d_temp",F.sum("count").over(windowval_2))


+---+--------+----------+-----+---------------+
| id|    name|      date|count|cum_sum_2d_temp|
+---+--------+----------+-----+---------------+
|  5|John Doe|2020-10-02|    1|              1|
|  2|John Doe|2020-11-27|    2|              2|
|  1|John Doe|2020-11-30|    1|              1|
|  4|John Doe|2020-12-01|    0|              1|
|  6|John Doe|2020-12-03|    1|              1|
|  7|John Doe|2020-12-04|    1|              2|
+---+--------+----------+-----+---------------+

What I am trying to do is when calculating the date range, the calculation excludes weekends i.e. in my table 2020-11-27 is a Friday and 2020-11-30 is Monday. The diff between them is 1 if we exclude Sat & Sun. I want the cumulative sum of 2020-11-27 and 2020-11-30 values in front of 2020-11-30 in the ‘cum_sum_2d_temp’ column which should be 3. I am looking to combine the solution to my earlier question to the date range.

Answer

Calculate the date_dif relative to the earliest date:

import numpy as np
import pyspark.sql.functions as F
from pyspark.sql.window import Window
from pyspark.sql.types import IntegerType

df = spark.createDataFrame([(1, "John Doe", "2020-11-30",1),(2, "John Doe", "2020-11-27",2),(4, "John Doe", "2020-12-01",0),(5, "John Doe", "2020-10-02",1),
                          (6, "John Doe", "2020-12-03",1),(7, "John Doe", "2020-12-04",1)],
                            ("id", "name", "date","count"))

workdaysUDF = F.udf(lambda date1, date2: int(np.busday_count(date2, date1)) if (date1 is not None and date2 is not None) else None, IntegerType())
df = df.withColumn("date_dif", workdaysUDF(F.col('date'), F.first(F.col('date')).over(Window.partitionBy('name').orderBy('date'))))

windowval = lambda days: Window.partitionBy('name').orderBy('date_dif').rangeBetween(-days, 0) 
df = df.withColumn("cum_sum",F.sum("count").over(windowval(2)))
df.show()

+---+--------+----------+-----+--------+-------+
| id|    name|      date|count|date_dif|cum_sum|
+---+--------+----------+-----+--------+-------+
|  5|John Doe|2020-10-02|    1|       0|      1|
|  2|John Doe|2020-11-27|    2|      40|      2|
|  1|John Doe|2020-11-30|    1|      41|      3|
|  4|John Doe|2020-12-01|    0|      42|      3|
|  6|John Doe|2020-12-03|    1|      44|      1|
|  7|John Doe|2020-12-04|    1|      45|      2|
+---+--------+----------+-----+--------+-------+