Regex-learner

This project provides a tool/library implementing an automated regular expression building mechanism.

This project takes inspiration on the paper from Ilyas, et al [1]

Ilyas, Andrew, M. F. da Trindade, Joana, Castro Fernandez, Raul and Madden, Samuel. 2018. "Extracting Syntactical Patterns from Databases."

This repository contains code and examples to assist in the exeuction of regular expression learning from the columns of data.

This is a basic readme. It will be completed as the prototype grows.

Installation

The project can be installed via pip:

pip install regex-learner

Examples of usage

Example of learning a date pattern from 100 examples of randomly sampled dates in the format DD-MM-YYYY.

from xsystem import XTructure
from faker import Faker

fake = Faker()
x = XTructure() # Create basic XTructure class

for _ in range(100):
    d = fake.date(pattern=r"%d-%m-%Y") # Create example of data - date in the format DD-MM-YYYY
    x.learn_new_word(d) # Add example to XSystem and learn new features

print(str(x)) # ([0312][0-9])(-)([01][891652073])(-)([21][09][078912][0-9])

Similary, the tool can be used directly from the command line using the regex-learner CLI provided by the installation of the package.

The tool has several options, as described by the help message:

> regex-learner -h
usage: regex-learner [-h] [-i INPUT] [-o OUTPUT] [--max-branch MAX_BRANCH] [--alpha ALPHA] [--branch-threshold BRANCH_THRESHOLD]

A simple tool to learn human readable a regular expression from examples

options:
  -h, --help            show this help message and exit
  -i INPUT, --input INPUT
                        Path to the input source, defaults to stdin
  -o OUTPUT, --output OUTPUT
                        Path to the output file, defaults to stdout
  --max-branch MAX_BRANCH
                        Maximum number of branches allowed, defaults to 8
  --alpha ALPHA         Weight for fitting tuples, defaults to 1/5
  --branch-threshold BRANCH_THRESHOLD
                        Branching threshold, defaults to 0.85, relative to the fitting score alpha

Assuming a data file containing the examples to learn from is called EXAMPLE_FILE, and assuming one is interested in a very simple regular expression, the tool can be used as follows:

cat EXAMPLE_FILE | regex-learner --max-branch 2

Note

Note that this project is not based on the actual implementation of the paper as presented in [2]

References

1. Ilyas, Andrew, et al. "Extracting syntactical patterns from databases." 2018 IEEE 34th International Conference on Data Engineering (ICDE). IEEE, 2018.
2. https://github.com/mitdbg/XSystem