06_csv_import

Example 06 — CSV import and export

What it demonstrates

The graph serialisation round-trip: read an edge-list CSV into the mutable adjlist builder with csv.ReadInto, then write the same graph back out in two interchange formats — CSV via csv.Write and newline-delimited JSON (JSON Lines / NDJSON) via jsonl.Write.

Domain / scenario

A three-edge directed cycle between three people. Each line of the input CSV is a src,dst,weight edge; the leading # line is a comment the reader skips:

# 3 example edges
alice,bob,1
bob,carol,2
carol,alice,3

The same graph is then emitted twice: once as CSV (one edge per row) and once as JSON Lines (one node record per node, then one edge record per edge). Both serialisations iterate nodes by ascending NodeID — which the mapper assigns in insertion order — so the output is byte-stable across runs and machines.

How to run

go run ./examples/06_csv_import

Expected output

Ingested 3 rows

CSV out:
alice,bob,1
bob,carol,2
carol,alice,3

JSON Lines out:
{"type":"node","id":"alice"}
{"type":"node","id":"bob"}
{"type":"node","id":"carol"}
{"type":"edge","src":"alice","dst":"bob","weight":1}
{"type":"edge","src":"bob","dst":"carol","weight":2}
{"type":"edge","src":"carol","dst":"alice","weight":3}

Key APIs

• graph/io/csv.ReadInto — parse an edge-list CSV (skipping # comments) into an adjlist.AdjList[string, int64], returning the row count.
• graph/io/csv.DefaultOptions — the default CSV layout (, delimiter, no header, # comment character).
• graph/io/csv.Write — serialise the adjacency list back to CSV, one edge per row.
• graph/io/jsonl.Write — serialise the same graph as JSON Lines: a node record per node followed by an edge record per edge.

Further reading

• graph/io/csv — CSV edge-list reader and writer
• graph/io/jsonl — JSON Lines reader and writer
• graph/adjlist — the mutable adjacency-list builder both formats target
• Example 01 — basic shortest paths — the minimal build-and-query flow
• docs/examples-standard.md — the standard every example follows