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Writing 835 files

oxedi.write turns tables into an 835 file. The tables can come from a parse, or be your own Arrow, Polars or pandas tables with the spec's columns.

To reproduce a parsed file byte for byte, you do not need the writer: use result.document.write() (see Reading).

Parse, change and write a file

This example changes the trace number of the example file and writes a new file:

import datetime
import polars as pl
import oxedi

result = oxedi.parse_file("remittance.835")
frames = result.tables.to_polars()   # {table name: polars frame}
frames["payments"] = frames["payments"].with_columns(trace_number=pl.lit("CHK100235"))

envelope = oxedi.Envelope(
    sender_id="ACMEPAYER",
    receiver_id="SUNRISECLINIC",
    date=datetime.date(2024, 1, 10),
    time=datetime.time(9, 0),
    usage_indicator="T",  # "P" (production) is the default
    line_break=True,
)
data = oxedi.write(frames, envelope, spec=result.spec)  # bytes, one interchange
print("\n".join(data.decode().splitlines()[:5]))  # the first five segments

ISA*00*          *00*          *ZZ*ACMEPAYER      *ZZ*SUNRISECLINIC  *240110*0900*^*00501*000000001*0*T*:~
GS*HP*ACMEPAYER*SUNRISECLINIC*20240110*0900*1*X*005010X221A1~
ST*835*0001~
BPR*I*690*C*CHK************20240112~
TRN*1*CHK100235*1512345678~
  • write returns the file as bytes. Save it with Path("out.835").write_bytes(data).
  • The writer is strict. If the money does not balance or the file would not read back clean, it raises oxedi.WriteError and writes nothing. See When the writer refuses a file.

Pass the right spec

The writer uses the spec that parsed the tables, else the built-in 5010 spec.

  • A dictionary of frames, as above, does not carry the parse's spec. Pass it: spec=result.spec (result.tables.spec is the same one).
  • For a 4010 file you can also pass oxedi.Spec.builtin("4010").

4010 files

Without the 4010 spec, a 4010 file is written as 5010 and refused.

Know what is written

  • A table you leave out has no rows. A column you leave out is null.
  • Rows nest by their payment, claim and service columns, the row number of their parent.
  • Only what the tables hold is written. Segments no column reads are left out, for example the payer's PER*CX or the bank details of BPR.
Details: the transaction header

The transaction set header carries no implementation convention reference, so a written 5010 header is ST*835*0001~.

Fill in the envelope

oxedi.Envelope gives what the tables cannot:

  • sender_id and receiver_id, with their qualifiers sender_qualifier and receiver_qualifier (default "ZZ").
  • date and time.
  • usage_indicator ("P" by default).
  • control_number, the first one (default 1).
  • application_sender and application_receiver, optional, for the group header.
  • delimiters: default *, :, ~ and repetition ^.
  • line_break: a line break after each segment.

The writer works out the rest:

  • The fixed-width ISA.
  • The control numbers that must match: ISA13/IEA02, GS06/GE02, ST02/SE02.
  • The counts: SE01, GE01, IEA01.

Write from SQL

The DuckDB extension writes the same file from SQL with COPY. For the same tables and envelope, the bytes equal those of oxedi.write. See Writing with COPY.

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