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Python bindings for MetroHash, a fast non-cryptographic hash algorithm

Project description

A Python wrapper around MetroHash

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Getting Started

To use this package in your program, simply type

pip install metrohash

After that, you should be able to import the module and do things with it (see usage example below).

Usage Examples

Stateless hashing

This package provides Python interfaces to 64- and 128-bit implementations of MetroHash algorithm. For stateless hashing, it exports metrohash64 and metrohash128 functions. Both take a value to be hashed and an optional seed parameter:

>>> import metrohash
...
>>> metrohash.metrohash64("abc", seed=0)
17099979927131455419
>>> metrohash.metrohash128("abc")
182995299641628952910564950850867298725

Incremental hashing

For incremental hashing, use MetroHash64 and MetroHash128 classes. Incremental hashing is associative and guarantees that any combination of input slices will result in the same final hash value. This is useful for processing large inputs and stream data. Example with two slices:

>>> mh = metrohash.MetroHash64()
>>> mh.update("Nobody inspects")
>>> mh.update(" the spammish repetition")
>>> mh.intdigest()
7851180100622203313

Note that the resulting hash value above is the same as in:

>>> mh = metrohash.MetroHash64()
>>> mh.update("Nobody inspects the spammish repetition")
>>> mh.intdigest()
7851180100622203313

Buffer protocol support

The methods in this module support Python Buffer Protocol, which allows them to be used on any object that exports a buffer interface. Here is an example showing hashing of a 4D NumPy array:

>>> import numpy as np
>>> arr = np.zeros((256, 256, 4))
>>> metrohash.metrohash64(arr)
12125832280816116063

Note that arrays need to be contiguous for this to work. To convert a non-contiguous array, use np.ascontiguousarray() method.

Development

For those who want to contribute, here is a quick start using some makefile commands:

git clone https://github.com/escherba/python-metrohash.git
cd python-metrohash
make env           # creates a Python virtualenv
make test          # run Python tests
make cpp-test      # run C++ tests

The Makefiles provided have self-documenting targets. To find out which targets are available, type:

make help

See Also

For other fast non-cryptographic hashing implementations available as Python extensions, see CityHash and MurmurHash.

Authors

The MetroHash algorithm and C++ implementation is due to J. Andrew Rogers. The Python bindings for it were written by Eugene Scherba.

License

This software is licensed under the Apache License, Version 2.0. See the included LICENSE file for details.

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Source Distribution

metrohash-0.1.1.tar.gz (63.6 kB view hashes)

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