T-Reg: A By-Example Regular Expression Generator

Version 0.000000000001

Created by Steve Johnson
[email protected]

Tested with Python 2.7
Should work with Python 2.6 (and 2.5 with minor modifications)

What It Does

T-Reg attempts to generate useful regular expressions from newline-delimited text files. For example, this input:

item 1: bananas
item 2: carrots

produces the regular expression ^item (\d+): (\w+)a(\w+)s$. (This is extremely early-stage output, and n strings will produce n-1 regular expressions.)

Usage

python treg.py <file name>

Planned features

• Options to ignore whitespace, specify comment characters, and give delimiter hints
• Much more processing of regex results
• Meta-regexes for higher level processing (It's turtles all the way down!)
• Interactive mode to make results more or less specific

How It Works

The current algorithm is stupidly simple:

• For each diff between each adjacent pair of lines
  • Begin with the string "^"
  • For each matching sequence, append an escaped string
  • For each pair of nonmatching sequences, append a capture group containing all characters found in both nonmatching sequences *Unless the nonmatching sequences contain a suspiciously regular set of characters like whitespace, letters, or numbers. In that case, append a specific kind of capture group relevant to the character set.
  • Append the string "$"
  • Output the string