Accept file objects in MODE_AUTO and check the database argument by oschwald · Pull Request #471 · maxmind/MaxMind-DB-Reader-python

oschwald · 2026-10-03T15:52:56Z

Lets MODE_AUTO read a file object and gives clear errors for a database argument that does not suit the mode.

File objects in MODE_AUTO. With the extension installed, MODE_AUTO passed every argument to the extension, which accepts only a path, so a file object raised TypeError. MODE_AUTO now reads a file object into memory with the pure Python reader, as MODE_FD does. A path object that also has a text read(), such as py.path.local, still opens as a path. A file descriptor still raises TypeError with the extension, as before.
Argument checks. The pure Python reader now raises TypeError with the fix for a path with MODE_FD, a file object with a path mode, a text-mode file, a read() that returns neither bytes nor an mmap, and a bool. Before, some of these raised AttributeError or an unrelated error. A descriptor object with __index__, such as numpy.int64, still works in the path modes.
Docs. The docstrings and README described MODE_FD as taking a file descriptor. They now say it takes a binary file object, and they note that a file object in MODE_AUTO uses the slower pure Python reader.

STF-1961

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Summary by CodeRabbit

New Features
- Database readers can now load data from binary file objects and file descriptors in supported modes, including automatic mode.
- Automatic mode uses the Python reader for file objects and follows the documented loading order for paths. File-object reads start at the current position.
- File objects remain open after reader creation; readers close file descriptors passed to supported modes.
Documentation
- Clarified supported input types, mode behavior, ownership and cleanup, and performance differences.

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coderabbitai · 2026-10-03T15:53:05Z

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tests/reader_test.py

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📝 Walkthrough

The reader now accepts binary file objects in MODE_AUTO and MODE_FD. It dispatches paths and descriptors according to the selected mode, validates file-object read results, and includes tests for supported inputs and error cases.

Changes: Reader input support

Layer / File(s)	Summary
Mode contract and dispatch `maxminddb/__init__.py`, `maxminddb/const.py`, `README.rst`, `HISTORY.rst`, `maxminddb/types.py`	The public API sends path inputs to the C reader when applicable and dispatches other inputs to the Python reader according to the mode. The documentation describes binary file-object support, path fallback order, and input ownership.
Reader input loading `maxminddb/reader.py`, `maxminddb/file.py`, `maxminddb/decoder.py`	The Python reader handles paths, integer-like descriptors, and readable objects according to the selected mode. File-object reads accept `bytes` or `bytearray`, and decoder buffer annotations include `bytearray`.
Input validation and mode tests `tests/reader_test.py`	Tests cover file objects, paths, descriptors, offsets, read results, and unsupported mode and input combinations.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant Caller
  participant open_database
  participant Reader
  participant BinaryFileObject
  Caller->>open_database: Pass binary file object with MODE_AUTO
  open_database->>Reader: Dispatch non-path input to Python reader
  Reader->>BinaryFileObject: Call read()
  BinaryFileObject-->>Reader: Return bytes or bytearray
  Reader-->>Caller: Return Reader

Merge Risk: 🔵 Low · up to 54de5

The reader now accepts binary file objects in automatic mode. The docstring may still not say who owns and closes the input, which is a small documentation gap that is worth clarifying before or shortly after merge.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 27.27% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 33 functions across 7 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely summarizes the main changes: support for file objects in MODE_AUTO and validation of database arguments.

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_{A rabbit reads a stream of bytes,
And checks each mode before it writes.
The paths and pipes take proper turns,
While bytearray joins what the reader learns.
The tests hop through each case with care,
Then leave the caller's stream right there.}

_{Comment @coderabbitai help to get the list of available commands.}

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Actionable comments posted: 1

🪄 Fix comments: Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
Review comments at @maxminddb/__init__.py:
- Around line 51-56: Update the ownership wording in the reader documentation to
specify that the reader closes a file descriptor, even when it is not a valid
database, and leaves a caller-provided file object open.

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HISTORY.rst
README.rst
maxminddb/__init__.py
maxminddb/const.py
maxminddb/decoder.py
maxminddb/file.py
maxminddb/reader.py
maxminddb/types.py
tests/reader_test.py

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MODE_AUTO passed every database argument to the C extension when it was installed, but the extension accepts only a path. A file object raised TypeError, although the pure Python reader can read it. Without the extension, a file object also raised TypeError. In MODE_AUTO, read a file object as MODE_FD does. A path still opens as a path, even if it also has read(), because some path objects, such as py.path.local, have a text read(). A file descriptor still raises TypeError with the extension, as before. The pure Python path modes close a descriptor, and a caller of the default mode might not expect that. Without the extension, MODE_AUTO still opens a descriptor, as before. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

MODE_FD calls database.read(), so it takes a binary file object, and MODE_AUTO now reads one the same way. The docstrings and the README said that MODE_FD takes a file descriptor. An int file descriptor fails with AttributeError in MODE_FD. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

_load_buffer passed the database argument to open(), FileBuffer and .read() behind 5 type: ignore comments, and it declared -> str although it returns the database argument or a file object name. An Any local hid that mismatch. The ignores hid real mismatches too. MODE_FD with a path raised AttributeError, and a path mode with a file object raised a TypeError from open() that did not name the mode. Check the argument type for the mode and raise TypeError with the fix. The checks narrow the type, so the ignores go away. FileBuffer now takes the path types that open() accepts. The unsupported mode check still comes first. The function returns object, because the caller only formats the name into error messages. One helper decides what is a file descriptor for both open_database and the pure Python reader. Error messages name the module of a type that is not a builtin, so that a zipfile.Path does not show as "Path". A text file that fails to decode in read() raises TypeError. A bytearray from read() stays a bytearray, as before, so the buffer and decoder types now include it. An mmap from read() still works, as in 3.2.0. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

The pure Python Reader accepts MODE_MMAP, but the error for an unsupported mode listed only MODE_AUTO, MODE_FILE, MODE_MEMORY and MODE_FD. A caller who passed MODE_MMAP_EXT was told that MODE_MMAP was not supported. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

The name for a file object without a name attribute was f"<{type(database)}>", so error messages showed "<<class '_io.BytesIO'>>". MODE_AUTO now reads file objects too, so these messages are more common. Use the type name, as in "<BytesIO>". Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

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oschwald mentioned this pull request Oct 3, 2026

Improve types and fix C extension crashes #465

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