Big data & Spark
PySpark jobs, partitioning, batch processing, and large-dataset transform patterns.
How to Implement row_number Window Function in Python
This code implements a SQL-style ROW_NUMBER() window function in pure Python, partitioning rows by a set of columns and ranking them within each partition by an ordered set of columns.
from collections import defaultdict
import itertools
def row_number(rows, partition_by, order_by):
partitions = defaultdict(list)
for index, row in enumerate(rows):
key = tuple(row[col] for col in partition_by)
partitions[key].append((index, row))
result = []
for key in partitions:
…Partition Data by Hash Key Mod N in Python
Returns a partition index for a string key by hashing it with MD5 and taking modulo N, then groups sample keys into partitions.
import hashlib
def partition_key(key: str, num_partitions: int) -> int:
"""Return partition index for key using MD5 hash mod N."""
digest = hashlib.md5(key.encode()).hexdigest()
return int(digest, 16) % num_partitions
if __name__ == "__main__":
keys = ["alice", "bob", "carol", "dave", "eve"]
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Big data & Spark — Python code examples
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