pyhash

Introduction

pyhash is a python non-cryptographic hash library.

It provides several common hash algorithms with C/C++ implementation for performance and compatibility.

>>> import pyhash
>>> hasher = pyhash.fnv1_32()

>>> hasher('hello world')
2805756500L

>>> hasher('hello', ' ', 'world')
2805756500L

>>> hasher('world', seed=hasher('hello '))
2805756500L

It also can be used to generate fingerprints without seed.

>>> import pyhash
>>> fp = pyhash.farm_fingerprint_64()

>>> fp('hello')
>>> 13009744463427800296L

>>> fp('hello', 'world')
>>> [13009744463427800296L, 16436542438370751598L]

Notes

hasher('hello', ' ', 'world') is a syntax sugar for hasher('world', seed=hasher(' ', seed=hasher('hello'))), and may not equals to hasher('hello world'), because some hash algorithms use different hash and seed size.

For example, metro hash always use 32bit seed for 64/128 bit hash value.

>>> import pyhash
>>> hasher = pyhash.metro_64()

>>> hasher('hello world')
>>> 5622782129197849471L

>>> hasher('hello', ' ', 'world')
>>> 16402988188088019159L

>>> hasher('world', seed=hasher(' ', seed=hasher('hello')))
>>> 16402988188088019159L

Installation

$ pip install pyhash

Notes

If pip install failed with similar errors, #27

/usr/lib/gcc/x86_64-linux-gnu/6/include/smmintrin.h:846:1: error: inlining failed in call to always_inline 'long long unsigned int _mm_crc32_u64(long long unsigned int, long long unsigned int)': target specific option mismatch
 _mm_crc32_u64 (unsigned long long __C, unsigned long long __V)
 ^~~~~~~~~~~~~
src/smhasher/metrohash64crc.cpp:52:34: note: called from here
             v[0] ^= _mm_crc32_u64(v[0], read_u64(ptr)); ptr += 8;
                     ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~

Please upgrade pip and setuptools to latest version and try again

$ pip install --upgrade pip setuptools

Notes

If pip install failed on MacOS with similar errors #28

   creating build/temp.macosx-10.6-intel-3.6
   ...
   /usr/bin/clang -fno-strict-aliasing -Wsign-compare -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -arch i386 -arch x86_64 -g -c src/smhasher/metrohash64crc.cpp -o build/temp.macosx-10.6-intel-3.6/src/smhasher/metrohash64crc.o -msse4.2 -maes -mavx -mavx2
    src/smhasher/metrohash64crc.cpp:52:21: error: use of undeclared identifier '_mm_crc32_u64'
                v[0] ^= _mm_crc32_u64(v[0], read_u64(ptr)); ptr += 8;
                        ^

You may try to

$ CFLAGS="-mmacosx-version-min=10.13" pip install pyhash

Notes

pyhash only support pypy v6.0 or newer, please download and install the latest pypy.

Algorithms

pyhash supports the following hash algorithms

• FNV (Fowler-Noll-Vo) hash
  • fnv1_32
  • fnv1a_32
  • fnv1_64
  • fnv1a_64
• MurmurHash
  • murmur1_32
  • murmur1_aligned_32
  • murmur2_32
  • murmur2a_32
  • murmur2_aligned_32
  • murmur2_neutral_32
  • murmur2_x64_64a
  • murmur2_x86_64b
  • murmur3_32
  • murmur3_x86_128
  • murmur3_x64_128
• lookup3
  • lookup3
  • lookup3_little
  • lookup3_big
• SuperFastHash
  • super_fast_hash
• City Hash _ city_32
  • city_64
  • city_128
  • city_crc_128
  • city_fingerprint_256
• Spooky Hash
  • spooky_32
  • spooky_64
  • spooky_128
• FarmHash
  • farm_32
  • farm_64
  • farm_128
  • farm_fingerprint_32
  • farm_fingerprint_64
  • farm_fingerprint_128
• MetroHash
  • metro_64
  • metro_128
  • metro_crc_64
  • metro_crc_128
• MumHash
  • mum_64
• T1Ha
  • t1ha2 (64-bit little-endian)
  • t1ha2_128 (128-bit little-endian)
  • t1ha1 (64-bit native-endian)
  • t1ha1_le (64-bit little-endian)
  • t1ha1_be (64-bit big-endian)
  • t1ha0 (64-bit, choice fastest function in runtime.)
  • t1_32
  • t1_32_be
  • t1_64
  • t1_64_be
• XXHash
  • xx_32
  • xx_64

String and Bytes literals

Python has two types can be used to present string literals, the hash values of the two types are definitely different.

• For Python 2.x String literals, str will be used by default, unicode can be used with the u prefix.
• For Python 3.x String and Bytes literals, unicode will be used by default, bytes can be used with the b prefix.

For example,

$ python2
Python 2.7.15 (default, Jun 17 2018, 12:46:58)
[GCC 4.2.1 Compatible Apple LLVM 9.1.0 (clang-902.0.39.2)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import pyhash
>>> hasher = pyhash.murmur3_32()
>>> hasher('foo')
4138058784L
>>> hasher(u'foo')
2085578581L
>>> hasher(b'foo')
4138058784L

$ python3
Python 3.7.0 (default, Jun 29 2018, 20:13:13)
[Clang 9.1.0 (clang-902.0.39.2)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import pyhash
>>> hasher = pyhash.murmur3_32()
>>> hasher('foo')
2085578581
>>> hasher(u'foo')
2085578581
>>> hasher(b'foo')
4138058784

You can also import unicode_literals to use unicode literals in Python 2.x

from __future__ import unicode_literals

In general, it is more compelling to use unicode_literals when back-porting new or existing Python 3 code to Python 2/3 than when porting existing Python 2 code to 2/3. In the latter case, explicitly marking up all unicode string literals with u'' prefixes would help to avoid unintentionally changing the existing Python 2 API. However, if changing the existing Python 2 API is not a concern, using unicode_literals may speed up the porting process.