Spark: Count number of duplicate rows

To count the number of duplicate rows in a pyspark DataFrame, you want to groupBy() all the columns and count(), then select the sum of the counts for the rows where the count is greater than 1:

import pyspark.sql.functions as funcs
df.groupBy(df.columns)\
    .count()\
    .where(funcs.col('count') > 1)\
    .select(funcs.sum('count'))\
    .show()

Via SO.