Python `Magika` Module

This guide provides documentation on how to use the magika Python module to identify file types from your code.

Tip

This section assumes you are familiar with the topics discussed in the Core Concepts section.

Quick Examples

The magika API is designed to be simple and intuitive. The following examples cover the most common use cases for identifying content from bytes, paths, and streams.

From bytes:

>>> from magika import Magika
>>> m = Magika()
>>> res = m.identify_bytes(b'function log(msg) {console.log(msg);}')
>>> print(res.output.label)
javascript

From a file path:

>>> from magika import Magika
>>> m = Magika()
>>> res = m.identify_path('./tests_data/basic/ini/doc.ini')
>>> print(res.output.label)
ini

From an open file stream:

>>> from magika import Magika
>>> m = Magika()
>>> with open('./tests_data/basic/ini/doc.ini', 'rb') as f:
>>>     res = m.identify_stream(f)
>>> print(res.output.label)
ini

API Reference

Instantiating Magika

First, create an instance of the Magika class. The constructor accepts several optional arguments to customize its behavior.

from magika import Magika, PredictionMode

# Default instantiation
magika = Magika()

# Custom instantiation
magika_custom = Magika(
    model_dir="/path/to/custom/model",
    prediction_mode=PredictionMode.BEST_GUESS,
    no_dereference=True,
)

Constructor Arguments:

• model_dir (Path, optional): Path to a directory containing a custom model. If not provided, defaults to the latest bundled model.
• prediction_mode (PredictionMode, optional): The prediction mode to use. Defaults to PredictionMode.HIGH_CONFIDENCE.
• no_dereference (bool, optional): If True, symbolic links will not be followed; their content type will be reported as symlink. Defaults to False.

Identifying Content

Once instantiated, the Magika object provides several methods for identifying content from different sources.

• magika.identify_bytes(bytes): Identifies the content type of an in-memory bytes object.
• magika.identify_path(path): Identifies the content type of a single file from its path (str | os.PathLike).
• magika.identify_paths(paths): Identifies the content type for a list of file paths.
• magika.identify_stream(stream): Identifies the content type from an already-open binary file-like object (e.g., the output of open(file_path, 'rb')). Note: 1) Magika will seek() around the stream; 2) the stream is not closed (closing is the responsibility of the caller).

If you are dealing with large files, the identify_path, identify_paths, and identify_stream variants are generally better: their implementation seek()s around the file/stream to extract the needed features, without loading the entire content in memory.

Performance with Large Files

For large files, the identify_path, identify_paths, and identify_stream methods are highly recommended. They are optimized to read only the necessary portions of the file by seeking within the file/stream, which avoids loading the entire content into memory. If your content is already loaded into a bytes object, identify_bytes is the most direct and efficient option.

Understanding the Result

All identify_* methods return a MagikaResult object. This object acts as a wrapper that contains the prediction details and the status of the operation. You should always check if the operation was successful before accessing the prediction.

>>> result = m.identify_path("path/to/file")
>>> if result.ok:
...     print(f"File is a {result.output.description}")
...     print(f"MIME Type: {result.output.mime_type}")
... else:
...     print(f"Error: {result.status.message}")

Data Models

The MagikaResult object and its nested data classes provide detailed information about the scan.

Consult the Understanding the Output section for more context.

MagikaResult

class MagikaResult:
    path: Path
    ok: bool
    status: Status
    prediction: MagikaPrediction
    # Shortcuts available only when result.ok is True
    dl: ContentTypeInfo
    output: ContentTypeInfo
    score: float

• ok (bool): True if the identification was successful, False otherwise.
• status (Status): Provides details on an error if ok is False.
• prediction (MagikaPrediction): The core prediction object, available only if ok is True.
• dl, output, score: For convenience, these are direct shortcuts to the corresponding fields within the prediction object.

MagikaPrediction

Contains the core deep learning model prediction and the final Magika output.

class MagikaPrediction:
    dl: ContentTypeInfo
    output: ContentTypeInfo
    score: float
    overwrite_reason: OverwriteReason

• dl (ContentTypeInfo): The raw prediction from the deep learning model.
• output (ContentTypeInfo): The final prediction from “Magika the tool,” which considers the model’s prediction, its confidence score, and the selected prediction mode. This is the result most users should rely on.
• score (float): The model’s confidence score (from 0.0 to 1.0).
• overwrite_reason (OverwriteReason): It indicates why the deep learning model’s prediction was overwritten (e.g., low confidence).

ContentTypeInfo

Contains detailed metadata about a predicted content type.

class ContentTypeInfo:
    label: ContentTypeLabel # e.g., "python"
    mime_type: str          # e.g., "text/x-python"
    group: str              # e.g., "code"
    description: str        # e.g., "Python source"
    extensions: List[str]   # e.g., ["py", "pyc"]
    is_text: bool           # e.g., True

ContentTypeLabel

A string enum (StrEnum) of all possible content type labels. Because it’s a StrEnum, its members can be used and compared just like regular strings.

class ContentTypeLabel(StrEnum):
    APK = "apk"
    BMP = "bmp"
    # ... and many more

Caution

ContentTypeLabel is a superset of supported types.

This enum is generated from our internal Content Types Knowledge Base and includes many types that the default model may not be trained to detect.

The presence of a label in this enum does not guarantee it can be a prediction result. To get the definitive list of possible output labels that “Magika the tool” can return, use the magika.get_output_content_types() method, discussed next.

Additional APIs

The Magika class also exposes a few helper methods:

• get_output_content_types(): Returns a list of all possible content type labels that Magika can return in the output.label field. This is the recommended way to get a definitive list of Magika’s possible outputs.
• get_model_content_types(): Returns a list of all possible content type labels the deep learning model can return (i.e., the possible values for dl.label, in addition to undefined). This is useful for debugging.
• get_module_version(): Returns the magika Python package version as a string.
• get_model_version(): Returns the name of the model being used as a string.

Development setup

This section is for contributors to the magika Python package.

• Project Management: magika uses uv for dependency management. To install all development dependencies, run: cd python; uv sync.

• Testing: To run the test suite, use pytest. You can exclude slow tests for faster runs: cd python; uv run pytest tests -m "not slow". Refer to the GitHub Actions workflows for more testing examples.

• Packaging: We use maturin to build the Python package, which combines the Rust-based CLI with the Python source code. This process is automated in our Build Python Package GitHub Action.