simplematch

Minimal, super readable string pattern matching for python.

import simplematch

simplematch.match("He* {planet}!", "Hello World!")
>>> {"planet": "World"}

simplematch.match("It* {temp:float}°C *", "It's -10.2°C outside!")
>>> {"temp": -10.2}

Installation

pip install simplematch

(Or just drop the simplematch.py file in your project.)

Syntax

simplematch has only two syntax elements:

• wildcard *
• capture group {name}

Capture groups can be named ({name}), unnamed ({}) and typed ({name:float}).

The following types are available:

• int
• float
• email
• url
• ipv4
• ipv6
• bitcoin
• ssn (social security number)
• ccard (matches Visa, MasterCard, American Express, Diners Club, Discover, JCB)

For now, only named capture groups can be typed.

Then use one of these functions:

import simplematch

simplematch.match(pattern, string) # -> returns a `dict` on match, `None` otherwise.
simplematch.test(pattern, string)  # -> returns `True` on match, `False` otherwise.

Or use a Matcher object:

import simplematch as sm

matcher = sm.Matcher(pattern)

matcher.match(string) # -> returns a dict or None
matcher.test(string)  # -> returns True / False
matcher.regex         # -> shows the generated regex

Basic usage

import simplematch as sm

# extracting data
sm.match(
    pattern="Invoice_*_{year}_{month}_{day}.pdf",
    string="Invoice_RE2321_2021_01_15.pdf")
>>> {"year": "2021", "month": "01", "day": "15"}

# test match only
sm.test("ABC-{value:int}", "ABC-13")
>>> True

Typed matches

import simplematch as sm

matcher = sm.Matcher("{year:int}-{month:int}: {value:float}")

# extracting data
matcher.match("2021-01: -12.786")
>>> {"year": 2021, "month": 1, "value": -12.786}

# month is no integer -> no match and return `None`.
matcher.match("2021-AB: Hello")
>>> None

# no extraction, only test for match
matcher.test("1234-01: 123.123")
>>> True

# show generated regular expression
matcher.regex
>>> '^(?P<year>[+-]?[0-9]+)\\-(?P<month>[+-]?[0-9]+):\\ (?P<value>[+-]?(?:[0-9]*[.])?[0-9]+)$'

# show registered converters
matcher.converters
>>> {'year': <class 'int'>, 'month': <class 'int'>, 'value': <class 'float'>}

Register your own types

You can register your own types to be available for the {name:type} matching syntax with the register_type function.

simplematch.register_type(name, regex, converter=str)

• name is the name to use in the matching syntax
• regex is a regular expression to match your type
• converter is a callable to convert a match (str by default)

Example

Register a smiley type to detect smileys (:), :(, :/) and getting their moods:

import simplematch as sm

def mood_convert(smiley):
    moods = {
        ":)": "good",
        ":(": "bad",
        ":/": "sceptic",
    }
    return moods.get(smiley, "unknown")

sm.register_type("smiley", r":[\)\(\/]", mood_convert)

sm.match("I'm feeling {mood:smiley} *", "I'm feeling :) today!")
>>> {"mood": "good"}

CLI Command

You can also install simplematch for use as a CLI command e.g. using pipx.

pipx install simplematch

Usage

usage: simplematch [-h] [--regex] pattern [strings ...]

positional arguments:
  pattern     A matching pattern
  strings     The string to match

options:
  -h, --help  show this help message and exit
  --regex     Show the generated regular expression

Example

Extract a date from a specific file name:

simplematch "Invoice_*_{year}_{month}_{day}.pdf" "Invoice_RE2321_2021_01_15.pdf"
>>> {"year": "2021", "month": "01", "day": "15"}

Background

simplematch aims to fill a gap between parsing with str.split() and regular expressions. It should be as simple as possible, fast and stable.

The simplematch syntax is transpiled to regular expressions under the hood, so matching performance should be just as good.

I hope you get some good use out of this!

Contributions

Contributions are welcome! Just submit a PR and maybe get in touch with me via email before big changes.

License

MIT