Introduction

A perfect hash function for a set S of keys maps all keys in S to different numbers. That means that for the set S, the hash function is collision-free, or perfect. Further, a perfect hash function is called "minimal" when it maps N keys to N consecutive integers, usually in the range from 0 to N-1. (PyPi perfect-hash Documentation)

We will use the program Perfect_hash.py to generate a minimal perfect hash function (in Python) for a given set of keys.

There are two ways to obtain the tool perfect_hash.py.

1. Install perfect_hash.py and Use It In A Python Program

pip install perfect-hash

What actually happens is the program perfect_hash.py is downloaded and made available as a Python module. At the end of the install messages the location of the installed program is displayed.

There are two ways to access it within a Python program...

import sys
from perfect_hash import main

sys.exit(main())

Note:
  a. This uses a Python program run the Python
     program perfect_hash.py
  b. Put program arguments on the command line

import perfect_hash as ph

ph.read_table(...)

Note: This code allow access to internal methods

2. Download perfect_hash.py and Use It On The Command line

Note: This may be the best and simplest way to use the tool.

You can get perfect_hash.py from the install step above or locate and download it from the web. Either way, copy it to the location of your choice. For example to use it ...

./perfect_hash.py  [options] KEYS_FILE [TMPL_FILE]

Note: you may need replace the first line of the file with "#!/usr/bin/python3" or something like it.

Examples

To see examples click HERE .

perfect_hash.py Documentation

To see the command line help click HERE .

For more information about the PyPi Perfect-Hash Project click HERE .

More perfect-hash Documentation .

Links

perfect_hash.py (code found on the web)
Create Minimum perfect hash for sparse 64-bit unsigned integer
perfection module (A module that creates perfect hash functions for a known set of integer inputs)
Generic Perfect Hash Generator
Hash function (Wikipedia)
Hashing Tutorial 6 - Introduction to Perfect Hashing (YouTube)
Hashing Tutorial 7 - Building Perfect Hashing (YouTube)
Build a Hash Table in Python With TDD
Python documentation: Testing for Python Keywords

GNU Perfect Hash Function Generator (Gperf)

Gperf Home
Gperf Manual
Gperf for Windows
Gperf Documentation