puremagic

puremagic is a pure python module that will identify a file based off its magic numbers. It has zero runtime dependencies and serves as a lightweight, cross-platform alternative to python-magic/libmagic.

It is designed to be minimalistic and inherently cross platform compatible. It is also designed to be a stand in for python-magic. It implements the functions from_file(filename[, mime]) and from_string(string[, mime]) however the magic_file() and magic_string() are more powerful and will also display confidence and duplicate matches.

Starting with version 2.0, puremagic includes a deep scan system that performs content-aware analysis beyond simple magic number matching. This improves accuracy for formats like Office documents, text files, CSV, MP3, Python source, JSON, HDF5, email, and many scientific formats. Deep scan is enabled by default and can be disabled by setting the environment variable PUREMAGIC_DEEPSCAN=0.

Advantages over using a wrapper for 'file' or 'libmagic':

Faster
Lightweight
Cross platform compatible
No dependencies

Disadvantages:

Does not have as many file types
No multilingual comments
Duplications due to small or reused magic numbers

(Help fix the first two disadvantages by contributing!)

Compatibility

Python 3.12+

For use with Python 3.7--3.11, use the 1.x release chain.

Using github ci to run continuous integration tests on listed platforms.

Install from PyPI

$ pip install puremagic

On linux environments, you may want to be clear you are using python3

$ python3 -m pip install puremagic

Usage

"from_file" will return the most likely file extension. "magic_file" will give you every possible result it finds, as well as the confidence.

import puremagic

filename = "test/resources/images/test.gif"

ext = puremagic.from_file(filename)
# '.gif'

puremagic.magic_file(filename)
# [['.gif', 'image/gif', 'Graphics interchange format file (GIF87a)', 0.7],
#  ['.gif', '', 'GIF file', 0.5]]

With "magic_file" it gives each match, highest confidence first:

possible extension(s)
mime type
description
confidence (All headers have to perfectly match to make the list, however this orders it by longest header, therefore most precise, first)

If you already have a file open, or raw byte string, you could also use:

from_string
from_stream
magic_string
magic_stream

with open(r"test\resources\video\test.mp4", "rb") as file:
    print(puremagic.magic_stream(file))

# [PureMagicWithConfidence(byte_match=b'ftypisom', offset=4, extension='.mp4', mime_type='video/mp4', name='MPEG-4 video', confidence=0.8),
#  PureMagicWithConfidence(byte_match=b'iso2avc1mp4', offset=20, extension='.mp4', mime_type='video/mp4', name='MP4 Video', confidence=0.8)]

Deep Scan

Deep scan performs content-aware analysis when magic number matching alone is not enough. It is enabled by default and runs automatically as part of the normal identification pipeline.

The following format-specific scanners are included:

ZIP --- Distinguishes Office formats (xlsx/docx/pptx), OpenDocument (odt/ods/odp), and their macro-enabled variants by inspecting ZIP internals
MPEG Audio --- Parses MP3/MPEG audio frames to validate and identify audio files
Text --- Detects text encodings, line endings (CRLF/LF/CR), CSV files with automatic delimiter detection, and email messages (.eml)
Python --- Validates Python source via ast.parse() and keyword analysis
PDF --- Format-specific PDF validation
JSON --- JSON format validation
HDF5 --- Identifies HDF5 subtypes used in scientific computing (AnnData, Loom, Cooler, BIOM v2, mz5, and more)
Audio --- Identifies HCOM and SNDR audio formats
Dynamic text checks --- Recognizes many scientific and bioinformatics text formats including VCF, SAM, GFF, PLY, VTK, and others

To disable deep scan, set the environment variable:

$ export PUREMAGIC_DEEPSCAN=0

Script

Usage

$ python -m puremagic [options] filename <filename2>...

Options

-m, --mime --- Return the MIME type instead of file extension
-v, --verbose --- Print verbose output with all possible matches
--version --- Show program version

Directories can be passed as arguments; all files within will be scanned.

Examples

$ python -m puremagic test/resources/images/test.gif
'test/resources/images/test.gif' : .gif

$ python -m puremagic -m test/resources/images/test.gif test/resources/audio/test.mp3
'test/resources/images/test.gif' : image/gif
'test/resources/audio/test.mp3' : audio/mpeg

Upgrading from 1.x

Version 2.0 includes the following breaking changes:

Python 3.12+ required --- Python 3.7--3.11 are no longer supported. Use the 1.x release chain for older Python versions.
Removed puremagic.what() --- The imghdr drop-in replacement has been removed. Use puremagic.from_file() instead.
Removed magic_header_array, magic_footer_array, and multi_part_dict from the public API.
Removed setup.py --- The project now uses pyproject.toml exclusively.
Internal functions have been renamed from private (e.g. _magic_data) to public (e.g. magic_data).

FAQ

The file type is actually X but it's showing up as Y with higher confidence?

This can happen when the file's signature happens to match a subset of a file standard. The subset signature will be longer, therefore report with greater confidence, because it will have both the base file type signature plus the additional subset one.

Acknowledgements

Gary C. Kessler

For use of his File Signature Tables, available at: https://filesig.search.org/

Freedesktop.org

For use of their shared-mime-info file, available at: https://cgit.freedesktop.org/xdg/shared-mime-info/