tha-map-runner 0.2.3

A Tabular Helper API library that maps and joins dict-like data into row dicts using dotted-path projection.

tha-map-runner

A small Python library that joins a list of row dicts with a lookup source, projecting values into flat row columns via a mapping config.

Supports single-key and composite-key joins, left/inner/anti modes, and dotted-path projection into arbitrarily nested source data.

Install

pip install tha-map-runner

Quick start

from tha_map_runner import ThaMap

mapper = ThaMap()

Single-key — match rows against a lookup source on one field:

rows = [
    {"Org BK": "school-001", "Start Date": "08/15"},
    {"Org BK": "school-002", "Start Date": "08/16"},
]

api_response = [
    {"sourcedId": "school-001", "name": "Lincoln Elementary", "parent": {"sourcedId": "dist-A"}},
    {"sourcedId": "school-002", "name": "Roosevelt Middle",   "parent": {"sourcedId": "dist-A"}},
]

enriched = mapper.enrich_rows(
    rows,
    source=api_response,
    mapping={
        "Org Name":  "name",
        "Parent BK": "parent.sourcedId",  # dotted path into nested source
    },
    row_key="Org BK",
    source_key="sourcedId",               # also supports dotted paths: "org.sourcedId"
)

Composite-key — all key pairs must match simultaneously (use when a single field is ambiguous):

rows = [
    {"source_id": "s-001", "student": "Alice", "Term": "Fall"},
    {"source_id": "s-001", "student": "Bob",   "Term": "Fall"},
]

api_response = [
    {"org": {"id": "s-001"}, "profile": {"name": "Alice"}, "grade": "A"},
    {"org": {"id": "s-001"}, "profile": {"name": "Bob"},   "grade": "B"},
]

enriched = mapper.enrich_rows(
    rows,
    source=api_response,
    mapping={"Grade": "grade"},
    keys=[
        {"row_key": "source_id", "source_key": "org.id"},
        {"row_key": "student",   "source_key": "profile.name"},
    ],
)

How it works

1. Builds an index of source keyed by the match field(s) — O(n+m), no nested loops
2. For each row, looks up a match; composite-key mode requires all pairs to agree
3. Walks dotted paths ("parent.sourcedId") into the matched source entry
4. Projects resolved values into new columns on a copy of the row
5. Returns a new list — input is never mutated

Rows whose row status is in skip_statuses are passed through unchanged.

API

ThaMap

ThaMap()

mapper.enrich_rows()

mapper.enrich_rows(
    rows,                              # list of row dicts
    source,                            # list of dicts to join against (any nesting depth)
    mapping,                           # {"output_column": "dotted.path"}
    row_key="",                        # column name in rows to match on (single-key mode)
    source_key="",                     # dotted path in source to match on (single-key mode)
    *,
    keys=None,                         # composite-key mode: [{"row_key": "...", "source_key": "..."}, ...]
    how="left",                        # "left" | "inner" | "anti"
    on_no_match="skip",                # "skip" | "error" | "blank"  (left only)
    allow_empty_source=False,          # if True, empty source is not an error
    skip_statuses=["error", "warning"],# rows with these statuses are passed through
) -> list[dict]

Provide either row_key + source_key (single-key) or keys (composite-key) — not both.

Both source_key and the source_key entries in keys support dotted paths into arbitrarily nested source data (e.g. "org.sourcedId"). row_key always matches against the flat row dict.

Composite-key example — match only when both fields agree simultaneously:

mapper.enrich_rows(
    rows,
    api_response,
    mapping={"Grade": "grade", "Score": "score"},
    keys=[
        {"row_key": "source_id", "source_key": "org.sourcedId"},
        {"row_key": "student",   "source_key": "student.profile.name"},
    ],
)

Results are also stored in mapper.rows.

mapper.enrich_from_ddb()

Enriches rows from a fetch_by_pk result (the {table_name: {pk: record}} shape returned by tha-aws-runner's ThaDdb.fetch_by_pk). No tha-aws-runner import required — just pass the dict.

mapper.enrich_from_ddb(
    rows,                              # list of row dicts
    ddb_result,                        # {table_name: {pk: record}} from ThaDdb.fetch_by_pk
    row_key,                           # column name in rows to match on (matched against pk)
    mapping,                           # {"output_column": "dotted.path"}
    *,
    table_name="",                     # scope lookup to one table (all rows same table)
    table_name_col="",                 # row column holding the table name (mixed-table rows)
    how="left",                        # "left" | "inner" | "anti"
    on_no_match="skip",                # "skip" | "error" | "blank"  (left only)
    skip_statuses=["error", "warning"],# rows with these statuses are passed through
) -> list[dict]

Provide exactly one of table_name or table_name_col — not both, not neither.

not_found entries in ddb_result are filtered automatically and treated as missing matches.

Single-table — all rows look up against the same table:

enriched = mapper.enrich_from_ddb(rows, all_ddb, "user_id", {"Name": "name"}, table_name="users_table")

Multi-table (chained) — one call per table, each scoped explicitly:

all_ddb = {**ddb.fetch_by_pk("users_table", user_ids, key_name="id", key_type="S"),
           **ddb.fetch_by_pk("orders_table", order_ids, key_name="id", key_type="S")}

enriched = mapper.enrich_from_ddb(rows, all_ddb, "user_id", {"Name": "name"}, table_name="users_table")
enriched = mapper.enrich_from_ddb(enriched, all_ddb, "order_id", {"Status": "status"}, table_name="orders_table")

Mixed-table rows — rows have different tables; use table_name_col to route each row:

rows = [
    {"pk": "user-001", "source_table": "users_table"},
    {"pk": "order-001", "source_table": "orders_table"},
]

enriched = mapper.enrich_from_ddb(rows, all_ddb, "pk", {"Name": "name"}, table_name_col="source_table")

Results are also stored in mapper.rows.

how

Value	Behaviour
"left"	All rows kept; unmatched rows handled by on_no_match
"inner"	Only matched rows kept; mapping applied
"anti"	Only unmatched rows kept; no mapping applied

Rows whose row status is in skip_statuses are always passed through unchanged, regardless of how.

on_no_match (left join only)

Value	Behaviour
"skip"	Row is returned unchanged — no new columns added
"error"	row status="error", message=..., mapping columns set to ""
"blank"	Mapping columns set to "", row status untouched

skip_statuses

By default, rows already marked row status="error" or row status="warning" are passed through without processing. Override with any list:

mapper.enrich_rows(..., skip_statuses=["error"])               # only skip errors
mapper.enrich_rows(..., skip_statuses=["error", "pending"])    # custom statuses
mapper.enrich_rows(..., skip_statuses=[])                      # process every row regardless

Composing with tha-csv-runner

from tha_csv_runner import ThaCSV
from tha_map_runner import ThaMap
import requests

runner = ThaCSV()
runner.read("Step 1 of 2", "input.csv", ["Org BK"])

api_response = requests.get(api_url).json()

mapper = ThaMap()
enriched = mapper.enrich_rows(
    rows=runner.rows,
    source=api_response,
    mapping={"Org Name": "name", "District": "parent.sourcedId"},
    row_key="Org BK",
    source_key="sourcedId",
)

runner.write("Step 2 of 2", "output.csv", rows=enriched)

Alternatives

This library is intentionally limited in scope — it handles one specific pattern: joining row dicts against a lookup list on a single key and projecting values via dotted paths. For more general needs:

• pandas — DataFrame.merge() covers join operations with far more flexibility (outer, multi-key, aggregations)
• glom — powerful dotted-path access and transformation for arbitrarily nested Python data structures
• jmespath — JSON path-style queries for extracting values from nested dicts

Choose this library when you're already working with tha-* row dicts and want to join them against a lookup list in one call — no DataFrame conversion, left/inner/anti join and projection in a single step.

License

MIT