pyspark create dictionary from data in two columns

Question

I have a pyspark dataframe with two columns:

[Row(zip_code='58542', dma='MIN'),
 Row(zip_code='58701', dma='MIN'),
 Row(zip_code='57632', dma='MIN'),
 Row(zip_code='58734', dma='MIN')]

How can I make a key:value pair out of the data inside the columns?

e.g.:

{
 "58542":"MIN",
 "58701:"MIN",
 etc..
}

I would like to avoid using collect for performance reasons. I've tried a few things but can't seem to get just the values.

Answer 1

You can simply do this:

dict = {row['zipcode']:row['dma'] for row in df.collect()}
print(dict)
#{'58542': 'MIN', '58701': 'MIN', '57632': 'MIN', '58734': 'MIN'}

Answer 2

You can avoid using a udf here using pyspark.sql.functions.struct and pyspark.sql.functions.to_json (Spark version 2.1 and above):

import pyspark.sql.functions as f
from pyspark.sql import Row

data = [
    Row(zip_code='58542', dma='MIN'),
    Row(zip_code='58701', dma='MIN'),
    Row(zip_code='57632', dma='MIN'),
    Row(zip_code='58734', dma='MIN')
]

df = spark.createDataFrame(data)

df.withColumn("json", f.to_json(f.struct("dma", "zip_code"))).show(truncate=False)
#+---+--------+--------------------------------+
#|dma|zip_code|json                            |
#+---+--------+--------------------------------+
#|MIN|58542   |{"dma":"MIN","zip_code":"58542"}|
#|MIN|58701   |{"dma":"MIN","zip_code":"58701"}|
#|MIN|57632   |{"dma":"MIN","zip_code":"57632"}|
#|MIN|58734   |{"dma":"MIN","zip_code":"58734"}|
#+---+--------+--------------------------------+

If you instead wanted the zip_code to be the key, you can create a MapType directly using pyspark.sql.functions.create_map:

df.withColumn("json", f.create_map(["zip_code", "dma"])).show(truncate=False)
#+---+--------+-----------------+
#|dma|zip_code|json             |
#+---+--------+-----------------+
#|MIN|58542   |Map(58542 -> MIN)|
#|MIN|58701   |Map(58701 -> MIN)|
#|MIN|57632   |Map(57632 -> MIN)|
#|MIN|58734   |Map(58734 -> MIN)|
#+---+--------+-----------------+

Answer 3

There is one more way to convert your dataframe into dict. for that you need to convert your dataframe into key-value pair rdd as it will be applicable only to key-value pair rdd. since dictionary itself a combination of key value pairs.

data = [
    Row(zip_code='58542', dma='MIN'),
    Row(zip_code='58701', dma='MIN'),
    Row(zip_code='57632', dma='MIN'),
    Row(zip_code='58734', dma='MIN')
]

>>> data.show();
+---+--------+
|dma|zip_code|
+---+--------+
|MIN|   58542|
|MIN|   58701|
|MIN|   57632|
|MIN|   58734|
+---+--------+

converting your dataframe into rdd.

newrdd = data.rdd

since you want zip_code as your key and dma as value, so have selected rdd element '1' as key and element '0' as value.

keypair_rdd = newrdd.map(lambda x : (x[1],x[0]))

once you have key-pair rdd then simply use collectAsMap to convert it into a dictonary

>>> dict = keypair_rdd.collectAsMap()
>>> print dict
{u'58542': u'MIN', u'57632': u'MIN', u'58734': u'MIN', u'58701': u'MIN'}

>>> dict.keys()
[u'58542', u'57632', u'58734', u'58701']

looks value for specific key:

>>> dict.get('58542')
u'MIN'