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Ultra-lightweight pure Python package to check if a file is binary or text.

Project description Documentation Status Updates

Ultra-lightweight pure Python package to guess whether a file is binary or text, using a heuristic similar to Perl’s pp_fttext and its analysis by @eliben.


It works, and people are using this package in various places. But it doesn’t cover all edge cases yet.

The code could be improved. Pull requests welcome! As of now, it is based on these snippets, but that may change:


Has tests for these file types:

  • Text: .txt, .css, .json, .svg, .js, .lua, .pl, .rst
  • Binary: .png, .gif, .jpg, .tiff, .bmp, .DS_Store, .eot, .otf, .ttf, .woff, .rgb

Has tests for numerous encodings.


You may be thinking, “I can write this in 2 lines of code?!”

It’s actually not that easy. Here’s a great article about how Perl’s heuristic to guess file types works:

And that’s just where we started. Over time, we’ve found more edge cases and our heuristic has gotten more complex.

Also, this package saves you from having to write and thoroughly test your code with all sorts of weird file types and encodings, cross-platform.


Linux (Ubuntu 12.04 LTS Server Edition 64 bit):

Windows (Windows Server 2012 R2 (x64)):



0.4.4 (2017-04-13)

  • Notify users for file i/o issues. Thanks @lukehinds!

0.4.3 (2017-04-13)

0.4.2 (2017-04-12)

0.4.0 (2015-08-21)

  • Enhanced detection for some binary streams and UTF texts. (#10, 11) Thanks @pombredanne.
  • Set up Appveyor for continuous testing on Windows. Thanks @pydanny.
  • Update link to Perl source implementation. (#9) Thanks @asmeurer @pombredanne @audreyr.
  • Handle UnicodeDecodeError in check. (#12) Thanks @DRMacIver.
  • Add very simple Hypothesis based tests. (#13) Thanks @DRMacIver.
  • Use setup to determine requirements and remove redundant requirements.txt. (#14) Thanks @hackebrot.
  • Add documentation status badge to README.rst. (#15) Thanks @hackebrot.
  • Run tox in travis.yml. Add pypy and Python 3.4 to tox environments. (#16) Thanks @hackebrot @pydanny.
  • Handle LookupError when detecting encoding. (#17) Thanks @DRMacIver.

0.3.0 (2014-05-05)

  • Include tests, docs in source package. (#6) Thanks @vincentbernat.
  • Drop unnecessary shebangs and executable bits. (#8) Thanks @scop.
  • Generate string of printable extended ASCII bytes only once. (#7) Thanks @scop.
  • Make number of bytes to read parametrizable. (#7) Thanks @scop.

0.2.0 (2013-09-22)

  • Complete rewrite of everything. Thanks @ncoghlan.

0.1.1 (2013-08-17)

  • Tests pass under Python 2.6, 2.7, 3.3, PyPy.

0.1.0 (2013-08-17)

  • First release on PyPI.

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