I'm trying to use filter to find those 'title' that are not in list_A.

A = B.groupBy("title").count()
A = A.filter(A['count'] > 1)
A_df = A.toPandas()
list_A = A_df['title'].values.tolist()
B.filter(~B.title.isin(list_A)).count()

However, I get an empty dataframe back (count is 0)

It works well when I use 'is in':

Why this happened and how can I solve this?

I tried:

B=B.na.drop(subset=["title"])
B.filter(~B.title.isin(list_A)).count()
print(B.filter(~B.title.isin(list_A) | B.title.isNull()).count())

It still returns 0.

CodePudding user response：

It may be because other "title" values are null.

B = spark.createDataFrame([('x',), ('x',), (None,)], ['title'])

A = B.groupBy("title").count()
A = A.filter(A['count'] > 1)
A_df = A.toPandas()
list_A = A_df['title'].values.tolist()

print(B.filter(~B.title.isin(list_A)).count())
# 0
print(B.filter(B.title.isin(list_A)).count())
# 2

If you really need list_A, you shouldn't go to Pandas for it.

• You can either use collect

  A = B.groupBy("title").count().filter(F.col('count') > 1)
  list_A = [x.title for x in A.collect()]
  print(list_A)
  # ['x', None]
  

• or collect_set

  list_A = (B
      .groupBy("title").count()
      .groupBy((F.col('count') > 1).alias('_c')).agg(
          F.collect_set('title').alias('_t')
      ).filter('_c')
      .head()[1]
  )
  print(list_A)
  # ['x']
  

Finally, to translate your current query to PySpark, you should use window functions.

Input:

from pyspark.sql import functions as F, Window as W
B = spark.createDataFrame(
    [('x', 'Example'),
     ('x', 'Example'),
     ('x', 'not_example'),
     ('y', 'not_example'),
     (None, 'not_example'),
     (None, 'Example')],
    ['title', 'journal'])

Your current script:

A = B.groupBy("title").count()
A = A.filter(A['count'] > 1)
A_df = A.toPandas()
list_A = A_df['title'].values.tolist()
B.filter(((B.title.isin(list_A))&(B.journal!="Example"))|(~B.title.isin(list_A)))

Suggestion:

B_filtered = (B
    .withColumn('A_cnt', F.count('title').over(W.partitionBy('title')))
    .filter("(A_cnt > 1 and journal != 'Example') or A_cnt <= 1")
    .drop('A_cnt')
)
B_filtered.show()
#  ----- ----------- 
# |title|    journal|
#  ----- ----------- 
# | null|not_example|
# | null|    Example|
# |    x|not_example|
# |    y|not_example|
#  ----- -----------