class pooch.Decompress(method='auto', name=None)[source]

Processor that decompress a file and returns the decompressed version.

Use with pooch.Pooch.fetch or pooch.retrieve to decompress a downloaded data file so that it can be easily opened. Useful for data files that take a long time to decompress (exchanging disk space for speed).

Supported decompression methods are LZMA (.xz), bzip2 (.bz2), and gzip (.gz).

File names with the standard extensions (see above) can use method="auto" to automatically determine the compression method. This can be overwritten by setting the method argument.


To unpack zip and tar archives with one or more files, use pooch.Unzip and pooch.Untar instead.

The output file is {fname}.decomp by default but it can be changed by setting the name parameter.


Passing in name can cause existing data to be lost! For example, if a file already exists with the specified name it will be overwritten with the new decompressed file content. Use this option with caution.

  • method (str) – Name of the compression method. Can be “auto”, “lzma”, “xz”, “bzip2”, or “gzip”.

  • name (None or str) – Defines the decompressed file name. The file name will be {fname}.decomp if None (default) or the given name otherwise. Note that the name should not include the full (or relative) path, it should be just the file name itself.

Methods Summary

Decompress.__call__(fname, action, pooch)

Decompress the given file.

Decompress.__call__(fname, action, pooch)[source]

Decompress the given file.

The output file will be either {fname}.decomp or the given name class attribute.

  • fname (str) – Full path of the compressed file in local storage.

  • action (str) –

    Indicates what action was taken by pooch.Pooch.fetch or pooch.retrieve:

    • "download": File didn’t exist locally and was downloaded

    • "update": Local file was outdated and was re-download

    • "fetch": File exists and is updated so it wasn’t downloaded

  • pooch (pooch.Pooch) – The instance of pooch.Pooch that is calling this.


fname (str) – The full path to the decompressed file.