Data Python active any

Python byte-oriented file work opens files in binary mode

data-python-018

Intent

Keep Python byte I/O from silently passing through text-mode transcoding.

Applicability

Applies to Python file or stream code handling bytes. Return unknown when the boundary object is supplied elsewhere.

What to inspect

open(...), mode strings, bytes reads or writes, and file handles passed to binary encoders or decoders.

Pass criteria

Byte-oriented reads and writes use binary mode such as rb or wb.

Fail criteria

Code reads or writes raw bytes through text-mode file handles.

Do not flag

Pure text I/O where str is the intended contract.

Confidence guidance

HIGH when bytes are used with text mode. MEDIUM when wrapper types may convert earlier. LOW when the payload type is not visible.

Remediation

Open byte streams in binary mode and keep text encoding explicit elsewhere.

Pass example

with open(path, "wb") as f:
    f.write(payload)

Fail example

with open(path, "w") as f:
    f.write(payload)