Divide function in pyspark - numpy

Question

Suppose I have this dataframe on PySpark:
df = spark.createDataFrame([
['red', 'banana', 1, 10], ['blue', 'banana', 2, 20], ['red', 'carrot', 3, 30],
['blue', 'grape', 4, 40], ['red', 'carrot', 5, 50], ['black', 'carrot', 6, 60],
['red', 'banana', 7, 70], ['red', 'grape', 8, 80]], schema=['color', 'fruit', 'v1', 'v2'])
I want to create a function that takes column v2 divided by column v1, with the condition:
import numpy as np
from pyspark.sql.functions import pandas_udf
#pandas_udf('long', PandasUDFType.SCALAR)
def pandas_div(a,b):
if b == 0:
return np.nan
else:
return (a/b)
However the result turn out to be like this
ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().
The output that I want should be like this:
+---------+---------+---+
|color_new|fruit_new|div|
+---------+---------+---+
| red| banana|10 |
| blue| banana|20 |
| red| carrot|30 |
| blue| grape|40 |
| red| carrot|50 |
| black| carrot|60 |
| red| banana|70 |
| red| grape|80 |
+---------+---------+---+

Answer 1

All you needed was a WHEN and OTHERWISE. See example below
# Create data frame
df = spark.createDataFrame([
['red', 'banana', 1, 10], ['blue', 'banana', 2, 20], ['red', 'carrot', 3, 30],
['blue', 'grape', 4, 40], ['red', 'carrot', 5, 50], ['black', 'carrot', 6, 60],
['red', 'banana', 7, 70], ['red', 'grape', 8, 80], ['orange', 'grapefruit', 0, 100]], schema=['color', 'fruit', 'v1', 'v2'])
# display result
df.show()
+------+----------+---+---+
| color| fruit| v1| v2|
+------+----------+---+---+
| red| banana| 1| 10|
| blue| banana| 2| 20|
| red| carrot| 3| 30|
| blue| grape| 4| 40|
| red| carrot| 5| 50|
| black| carrot| 6| 60|
| red| banana| 7| 70|
| red| grape| 8| 80|
|orange|grapefruit| 0|100|
+------+----------+---+---+
# Import functions
import pyspark.sql.functions as f
# apply case when
df1 = df.withColumn("divide", f.when(f.col("v1") == 0, None).otherwise(f.lit(f.col("v2")/f.col("v1"))))
# display result
df1.show()
+------+----------+---+---+------+
| color| fruit| v1| v2|divide|
+------+----------+---+---+------+
| red| banana| 1| 10| 10.0|
| blue| banana| 2| 20| 10.0|
| red| carrot| 3| 30| 10.0|
| blue| grape| 4| 40| 10.0|
| red| carrot| 5| 50| 10.0|
| black| carrot| 6| 60| 10.0|
| red| banana| 7| 70| 10.0|
| red| grape| 8| 80| 10.0|
|orange|grapefruit| 0|100| null|
+------+----------+---+---+------+