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CSV Module

The py.csv standard library module provides relational predicates for parsing and generating CSV data. CSV records with headers map to DictTerm for unification-aware access.

The implementation lives in clausal/modules/py/csv.py.

Import

-import_from(py.csv, [Parse, ParseRow, ParseRecords, Generate,
                      GenerateRecords, ReadFile, ReadRecords, WriteFile])

Or via module import:

-import_module(py.csv)
# then use py.csv.ReadFile("data.csv", ROWS_), etc.

Type Mapping

  • CSV rows → Python list of str
  • CSV with headers → list of DictTerm (one per record)
  • All values are strings — no automatic type coercion. Use ++int(X) or number_chars for conversion.

Predicates

ParseRow/2

ParseRow(String, Row) — parse a single CSV line into a list of strings. Handles quoting.

parse_line(LINE, FIELDS) <- ParseRow(LINE, FIELDS)

Parse/2

Parse(String, Rows) — parse a multi-line CSV string into a list of rows (each row a list of strings).

ParseRecords/3

ParseRecords(String, Headers, Records) — parse CSV with the first row as headers. Each record is a DictTerm with header keys.

-import_from(py.csv, [ParseRecords])
-import_from(py.json, [Get])

parse_and_get_name(CSV_TEXT, NAME) <- (
    ParseRecords(CSV_TEXT, HEADERS, RECORDS),
    Member(RECORD, RECORDS),
    Get(RECORD, "name", NAME)
)

Generate/2

Generate(Rows, String) — serialize a list of rows (lists of values) to a CSV string. Values with commas are automatically quoted.

GenerateRecords/3

GenerateRecords(Headers, Records, String) — serialize DictTerm records with a header row.

ReadFile/2

ReadFile(Path, Rows) — read and parse a CSV file into a list of rows. Fails on file error.

ReadRecords/2

ReadRecords(Path, Records) — read a CSV file with headers, returning a list of DictTerms.

load_data(RECORDS) <- ReadRecords("data.csv", RECORDS)

WriteFile/2

WriteFile(Path, Rows) — serialize rows and write to a CSV file. Fails if rows contain unbound variables.

Example

-import_from(py.csv, [ReadRecords, ParseRow, Generate])

load_data(RECORDS) <- ReadRecords("data.csv", RECORDS)

parse_line(LINE, ROW) <- ParseRow(LINE, ROW)

export_rows(ROWS, CSV) <- Generate(ROWS, CSV)