rgx · PyPI

Typed, simple and readable regexp generation

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Project description

Many people complain about unreadable and complex syntax of regular expressions.
Many others complain about how they can't remember all constructs and features.

rgx solves those problems: it is a straightforward regexp builder. It also places parens where needed to respect intended operator priority.
It can produce a regular expression string to use in re.compile or any other regex library of your choice.

In other words, with rgx you can build a regular expression from parts, using straightforward and simple expressions.

Installation

pip install rgx

That's it.

Basic usage

Hello, regex world

import rgx
import re

word = rgx.meta.WORD_CHAR.many().capture() # (\w+), a capturing group
comma = rgx.pattern(",").maybe()

regex = rgx.pattern((
    "hello",
    comma,
    rgx.meta.WHITESPACE,
    (
        word + rgx.meta.WHITESPACE
    ).maybe(),
    "world"
)) # (?:hello,?\s(?:(\w+)\s)?world)

re.compile(
    regex.render_str("i") # global flag (case-insensitive)
)

Match some integers

this regex will match valid Python integer literals:

import rgx
import re

nonzero = rgx.char_range("1", "9") # [1-9]
zero = "0"
digit = zero | nonzero # 0|[1-9]
integer = zero | (nonzero + digit.some()) # 0|[1-9](?:0|[1-9])*

int_regex = re.compile(str(integer))

...or this one:

import rgx
import re

nonzero = rgx.char_range("1", "9") # [1-9]
digit = rgx.meta.DIGIT # \d
integer = digit | (nonzero + digit.some()) # \d|[1-9]\d*

int_regex = re.compile(str(integer))

Quickstart

in this readme, x means some pattern object. Occasionaly, y is introduced to mean some other pattern object (or literal)

Literals and pattern objects

rgx operates mostly on so-called "pattern objects" — rgx.entities.RegexPattern istances.
Your starting point would be rgx.pattern — it creates pattern objects from literals (and from pattern objects, which doesn't make a lot of sense).

rgx.pattern(str, escape: bool = True) creates a literal pattern — one that exactly matches given string. If you want to disable escaping, pass escape=False
rgx.pattern(tuple[AnyRegexPattern]) creates a non-capturing group of patterns (nested literals will be converted too)
rgx.pattern(list[str]) creates a character class (for example, rgx.pattern(["a", "b", "c"]) creates pattern [abc], that matches any character of those in brackets)

Most operations with pattern objects support using Python literals on one side, for example: rgx.pattern("a") | b would produce a|b pattern object (specifically, rgx.entities.Option)

Rendering patterns

import rgx

x = rgx.pattern("x")
pattern = x | x

rendered_with_str = str(pattern) # "x|x"
rendered_with_method = pattern.render_str() # "x|x"
rendered_with_method_flags = pattern.render_str("im") # (?im)x|x

Capturing Groups

import rgx

x = rgx.pattern("x")

print(x.capture()) # (x)

print(rgx.reference(1)) # \1


named_x = x.named("some_x") # x.named(name: str)

print(named_x) # (?P<some_x>x)

named_x_reference = rgx.named("some_x")

print(named_x_reference) # (?P=x)

To create a capturing group, use x.capture(), or rgx.reference(group: int) for a reference.
To create a named capturing group, use rgx.named(name: str, x), or rgx.named(name: str) for a named reference.

Character classes

import rgx


az = rgx.char_range("a", "z") # rgx.char_range(start?: str, stop?: str)
print(az) # [a-z]

digits_or_space = rgx.pattern(["1", "2", "3", rgx.meta.WHITESPACE]) 
print(digits_or_space) # [123\s]

print(az | digits_or_space) # [a-z123\s]

# [^a-z123\s]
print(
    (az | digits_or_space).reverse() # rgx.entities.Chars.reverse(self)
)

Conditional pattern

import rgx

x = rgx.pattern("x")
y = rgx.pattern("y")
z = rgx.pattern("z")

capture = x.capture()

# (x)(?(1)y|z)
print(
    capture + rgx.conditional(1, y, z)
)

Docs

Pattern methods

`pattern.render_str(flags: str = '') -> str`

Renders given pattern into a string with specified global flags.

`pattern.set_flags(flags: str) -> LocalFlags`

This method adds local flags to given pattern

x.flags("y") # "(?y:x)"

`pattern.concat(other: AnyRegexPattern) -> Concat`

Use to match one pattern and then another.

A.concat(B) is equivalent to A + B (works if either A or B is a RegexPart object, not a Python literal)

x.concat(y) # "xy"
x + y # "xy"

`pattern.option(other: AnyRegexPattern) -> Option`

Use to match either one pattern or another.

A.option(B) is equivalent to A | B (if either A or B is a RegexPart object, not a Python literal)

x.option(y) # "x|y"
x | y # "x|y"