# pyspark.RDD.foldByKey¶

RDD.foldByKey(zeroValue, func, numPartitions=None, partitionFunc=<function portable_hash>)[source]

Merge the values for each key using an associative function “func” and a neutral “zeroValue” which may be added to the result an arbitrary number of times, and must not change the result (e.g., 0 for addition, or 1 for multiplication.).

Examples

>>> rdd = sc.parallelize([("a", 1), ("b", 1), ("a", 1)])