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Speed up shutil.copyfile by using sendfile system call

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Latest version Tests status Coverage Supported Python versions

pyfastcopy is a simple Python module that monkey patches the shutil.copyfile function of Python standard library to internally use the sendfile system call.

It can provide important performance improvements for large file copy (typically 30-40%). See the performance section for some numbers.

Because shutil.copyfile is used by other fonctions in the shutil module, the following functions also automatically benefit from the performance boost:

  • shutil.copy

  • shutil.copy2

  • shutil.copytree

If sendfile is not available on your system or fails, the classic, slower chunk file copy is used, so there is no downside to using this module.

For more information, see my proposed patch for Python.


Tests were done copying files (source and destination) on a tmpfs filesystem, so that no slowdown related to hard drive or SSD storage occurs. Test files were generated with pseudo random data using frandom.

See for details about the test procedure and how the following graphs were generated.

Python 3.4: graph1 graph2 graph3

Python 3.6: graph4 graph5 graph6

These tests show a 30-50% performance improvement of ``shutil.copyfile`` compared to stock Python.


Just import the module:

import pyfastcopy

And then use the patched shutil.copyfile as usual:

shutil.copyfile(src, dst)

The ``sendfile`` system call does not exist on Windows, so importing this module will have no effect.


From PyPI (with PIP)

  1. If you don’t already have it, install pip for Python 3 (not needed if you are using Python >= 3.4)

  2. Install pyfastcopy: pip3 install pyfastcopy

  3. Enjoy fast copy when using shutil.copyfile, shutil.copy, shutil.copy2 or shutil.copytree

From source

  1. If you don’t already have it, install setuptools for Python 3

  2. Clone this repository: git clone

  3. Install pyfastcopy: python3 install

  4. Enjoy fast copy when using shutil.copyfile, shutil.copy, shutil.copy2 or shutil.copytree


Python Software Foundation License

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