rexplain

Explain, test, and generate examples for regular expressions.

Overview

rexplain is a Python toolkit for understanding, testing, and generating examples for regular expressions. It provides:

• Human-readable, line-by-line explanations of regex patterns
• Example string generation for any regex
• Detailed match testing with feedback
• Visual railroad diagrams for regex patterns
• Both a Python API and a CLI

Features

• Regex Explanation: Get clear, context-aware explanations for any regex pattern
• Test Regex: Test if a string matches a pattern and see why/why not
• Generate Examples: Generate example strings that match a regex
• Visual Diagrams: Generate railroad diagrams to visualize regex patterns
• CLI & API: Use from the command line or as a Python library
• Regex Flags: Supports Python regex flags (e.g., re.IGNORECASE)

Installation

pip install rexplain

Quick Start

CLI Usage

Explain a regex pattern:

rexplain explain "^\d{3}-\d{2}-\d{4}$"

Generate example strings:

rexplain examples "[A-Za-z]{5}" --count 3

Test if a string matches a pattern:

rexplain test "^hello.*" "hello world!"

Generate a railroad diagram:

rexplain diagram "^\\w+$" --output diagram.svg
rexplain diagram "^\\w+$" --detailed --output detailed.svg

Python API Usage

from rexplain import explain, examples, test, diagram

print(explain(r"\d+"))
print(examples(r"[A-Z]{2}\d{2}", count=2))
print(test(r"foo.*", "foobar"))

# Generate diagrams
diagram(r"^\w+$", "simple.svg")
diagram(r"^\w+$", "detailed.svg", detailed=True)
svg_content = diagram(r"^\w+$")  # Returns SVG as string

Example: Detailed Explanation

from rexplain import explain
print(explain(r"abc\w+\w*10$"))
# Output:
# a - matches the character 'a' (ASCII 97) literally (case sensitive)
# b - matches the character 'b' (ASCII 98) literally (case sensitive)
# c - matches the character 'c' (ASCII 99) literally (case sensitive)
# \w+ - matches a word character one or more times (greedy)
# \w* - matches a word character zero or more times (greedy)
# 1 - matches the character '1' (ASCII 49) literally (case sensitive)
# 0 - matches the character '0' (ASCII 48) literally (case sensitive)
# $ - asserts position at the end of a line

API Reference

explain(pattern: str, flags: int = 0) -> str

Returns a line-by-line explanation of the regex pattern.

examples(pattern: str, count: int = 3, flags: int = 0) -> List[str]

Generates example strings that match the pattern.

test(pattern: str, test_string: str, flags: int = 0) -> dict

Tests if a string matches the pattern and explains why/why not.

diagram(pattern: str, output_path: str = None, detailed: bool = False) -> str

Generates a railroad diagram for the regex pattern. Returns SVG content or saves to file.

Contributing

Contributions are welcome! To contribute:

• Fork the repo and create a branch
• Add or improve features/tests/docs
• Run tests
• Open a pull request

Running Tests & Coverage

To run all tests with coverage (threshold: 90%):

pip install .[test]
pytest

If coverage is below 90%, pytest will fail. Coverage details will be shown in the terminal.

License

MIT