When working with time series data, it is often necessary to calculate the time difference between two dates. Apache Spark provides an extensive collection of functions to perform date-time manipulations, and months_between is one of them. This function computes the number of months between two dates. If the first date (date1) is later than the second one (date2), the result will be positive. Notably, if both dates are on the same day of the month, the function will return a precise whole number. This article will guide you on how to utilize this function in PySpark.
Firstly, we need to create a SparkSession, which is the entry point to any functionality in Spark.
from pyspark.sql import SparkSession
# Initialize SparkSession
spark = SparkSession.builder.getOrCreate()Let’s create a DataFrame with hardcoded dates for illustration purposes. We’ll create two columns, date1 and date2, which will contain our dates in string format.
data = [("2023-07-04", "2022-07-04"),
("2023-12-31", "2022-01-01"),
("2022-02-28", "2021-02-28")]
df = spark.createDataFrame(data, ["date1", "date2"])
df.show()
Output
+----------+----------+
| date1| date2|
+----------+----------+
|2023-07-04|2022-07-04|
|2023-12-31|2022-01-01|
|2022-02-28|2021-02-28|
+----------+----------+
In this DataFrame, date1 is always later than date2. Now, we need to convert the date strings to date type using the to_date function.
from pyspark.sql.functions import col, to_date
df = df.withColumn("date1", to_date(col("date1"), "yyyy-MM-dd"))
df = df.withColumn("date2", to_date(col("date2"), "yyyy-MM-dd"))
df.show()
Let’s use the months_between function to calculate the number of months between date1 and date2.
from pyspark.sql.functions import months_between
df = df.withColumn("months_between", months_between("date1", "date2"))
df.show()
Result
+----------+----------+--------------+
| date1| date2|months_between|
+----------+----------+--------------+
|2023-07-04|2022-07-04| 12.0|
|2023-12-31|2022-01-01| 23.96774194|
|2022-02-28|2021-02-28| 12.0|
+----------+----------+--------------+
months_between returns a floating-point number indicating the number of months between the two dates. The function considers the day of the month as well, hence for the first and the last row where the day of the month is the same for date1 and date2, the returned number is a whole number.
Spark important urls to refer
