Extract String from text pyspark

Question

I have a pyspark dataframe:

Example:

text <String>                 |   name <String>  |   original_name <String>
----------------------------------------------------------------------------
HELLOWORLD2019THISISGOOGLE    |   WORLD2019      |   WORLD_2019
----------------------------------------------------------------------------
NATUREISVERYGOODFORHEALTH     |   null           |   null  
----------------------------------------------------------------------------
THESUNCONTAINVITAMIND         |   VITAMIND       |   VITAMIN_D
----------------------------------------------------------------------------
BECARETOOURHEALTHISVITAMIND   |   OURHEALTH      |   OUR_/HEALTH
----------------------------------------------------------------------------

I want to loop the name column and look if name values exists in text, if yes, I create a new_column, will be contain the original_name value of the name values found in text. Knowing that some times the dataframe columns are null.

Example:

• in the line 4 in the dataframe example, the text contain 2 values from name column: [OURHEALTH, VITAMIND], I should take its original_name values and store them in a new_column.

• in the line 2, the text contain OURHEALTH from name column, I should store in the new_column the original name value that found ==> [OUR_/HEALTH]

Expect result:

text <String>                 |   name <String>  |   original_name <String>  | new_column <Array>
------------------------------|------------------|---------------------------|----------------------------
HELLOWORLD2019THISISGOOGLE    |   WORLD2019      |   WORLD_2019              |  [WORLD_2019]
------------------------------|------------------|---------------------------|----------------------------
NATUREISVERYGOODFOROURHEALTH  |   null           |   null                    |  [OUR_/HEALTH]
------------------------------|------------------|---------------------------|----------------------------
THESUNCONTAINVITAMIND         |   VITAMIND       |   VITAMIN_D               |  [VITAMIN_D]
------------------------------|------------------|---------------------------|----------------------------
BECARETOOURHEALTHISVITAMIND   |   OURHEALTH      |   OUR_/HEALTH             |  [OUR_/HEALTH, VITAMIN_D ]
-----------------------------------------------------------------------------|----------------------------

I hope that I was clear in my explanation.

I tried by the following code:

df = df.select("text", "name", "original_name").agg(collect_set("name").alias("name_array"))
for name_item in name_array:    
    df.withColumn("new_column", F.when(df.text.contains(name_item), "original_name").otherwise(None))

Someone can help me please ? Thank you

Answer 1

One simple solution is to use join between the original DataFrame and a derived DataFrame with just the name column. As the join condition could be satisfied by multiple rows, we'll have to groupby the original column after join.

Here is a detailed example for your input :

data = [
    ("HELLOWORLD2019THISISGOOGLE", "WORLD2019", "WORLD_2019"),
    ("NATUREISVERYGOODFOROURHEALTH", None, None),
    ("THESUNCONTAINVITAMIND", "VITAMIND", "VITAMIN_D"),
    ("BECARETOOURHEALTHISVITAMIND", "OURHEALTH", "OUR_ / HEALTH")
]
df = spark.createDataFrame(data, ["text", "name", "original_name"])

# create new DF with search words
# as it's the originl_name which interests us for the final list so we select it too
search_df = df.select(struct(col("name"), col("original_name")).alias("search_match"))

# join on df.text contains search_df.name
df_join = df.join(search_df, df.text.contains(search_df["search_match.name"]), "left")

# group by original columns and collect matches in a list
df_join.groupBy("text", "name", "original_name")\
    .agg(collect_list(col("search_match.original_name")).alias("new_column"))\
    .show(truncate=False)

Output:

+----------------------------+---------+-------------+--------------------------+
|text                        |name     |original_name|new_column                |
+----------------------------+---------+-------------+--------------------------+
|HELLOWORLD2019THISISGOOGLE  |WORLD2019|WORLD_2019   |[WORLD_2019]              |
|THESUNCONTAINVITAMIND       |VITAMIND |VITAMIN_D    |[VITAMIN_D]               |
|NATUREISVERYGOODFOROURHEALTH|null     |null         |[OUR_ / HEALTH]           |
|BECARETOOURHEALTHISVITAMIND |OURHEALTH|OUR_ / HEALTH|[VITAMIN_D, OUR_ / HEALTH]|
+----------------------------+---------+-------------+--------------------------+