human-regex

Overview

Regular expressions for humans.

The human-regex package provides the classes StringRegex and BytesRegex which are subclasses of str or bytes, respectively. They contain methods and properties which can produce your regular expressions with readable code.

from human_regex import StringRegex as Sre

regex = Sre("match")
assert regex == "match"

regex = regex.not_preceded_by("element")
assert regex == "(?<!element)match"

regex = regex.named("my_group")
assert regex == "(?P<my_group>(?<!element)match)"

regex = Sre("match").not_preceded_by("element").named("my_group").optional
assert regex == "(?P<my_group>(?<!element)match)?"

Let's construct regular expressions for words ending in with the letter "c" and also for words starting with the letter "a":

from human_regex import StringRegex as Sre

word = Sre(r"\w").zero_or_more
assert word == r"\w*"

word_endswith_c = word.append("c").named("ends_with_c").prepend(r"\b").append(r"\b")
assert word_endswith_c == r"\b(?P<ends_with_c>\w*c)\b"

word_startswith_a = word.prepend("a").named("starts_with_a").prepend(r"\b").append(r"\b")
assert word_startswith_a == r"\b(?P<starts_with_a>a\w*)\b"

• Full Documentation

Subclasses of str, bytes

StringRegex and BytesRegex are subclasses of str or bytes, respectively. They interoperate with these objects seamlessly. Here are some alternative ways how to construct the pattern from the previous example in the Overview section. Here we mix StringRegex and str instances:

from human_regex import StringRegex as Sre

word = Sre(r"\w")
word += "*"
assert word == r"\w*"
assert isinstance(word, Sre)
assert isinstance(word, str)

word_endswith_c: str = "".join((r"\b", "(?P<ends_with_c>", word, "c", ")", r"\b"))
word_endswith_c: Sre = Sre(word_endswith_c)
# same as:
word_endswith_c: Sre = Sre("").join((r"\b", "(?P<ends_with_c>", word, "c", ")", r"\b"))
word_endswith_c: Sre = Sre.concatenate((r"\b", "(?P<ends_with_c>", word, "c", ")", r"\b"))

Proxy re Module's Functions and Flags

StringRegex and BytesRegex objects proxy the class re.RegexFlag and all flags and functions of the built-in re module (i.e. re.compile, re.search, etc.). These fuctions automatically take the StringRegex or BytesRegex instance object as their first argument:

from human_regex import StringRegex as Sre
import re  # needed only for the assert statements below

assert Sre.RegexFlag is re.RegexFlag

sre = Sre("abc.")
# Use the proxied `re.compile` function of the StringRegex instance
# and the proxied flags on the StringRegex class
compiled = sre.compile(flags=Sre.IGNORECASE | Sre.DOTALL)
# same as:
# compiled = re.compile(sre, flags=re.IGNORECASE | re.DOTALL)
assert isinstance(compiled, re.Pattern)

text = "abc\nABCd\n\Abc"

found = sre.findall(text, flags=Sre.IGNORECASE | Sre.DOTALL)
# same as:
# found = re.findall(sre, text, flags=re.IGNORECASE | re.DOTALL)
assert found == ["abc\n", "ABCd"]

StringRegex and BytesRegex

Every method demonstated with StringRegex is available on BytesRegex and is applicable to bytes objects, rather than str objects:

from human_regex import StringRegex as Sre, BytesRegex as Bre
import re  # needed only for the assert statements below

string_re = Sre("abc.").named("my_group")
string_pattern = string_re.compile(flags=Sre.IGNORECASE | Sre.DOTALL)
assert isinstance(string_pattern, re.Pattern)

bytes_re = Bre(b"abc.").named(b"my_group")
bytes_pattern = bytes_re.compile(flags=Bre.IGNORECASE | Bre.DOTALL)
assert isinstance(bytes_pattern, re.Pattern)

assert string_pattern.flags == 50 # includes the implicit Sre.UNICODE flag
assert bytes_pattern.flags == 18 # bytes patterns cannot use the UNICODE flag
assert (Bre.IGNORECASE | Bre.DOTALL | Bre.UNICODE).value == 50

Caution When Iterating Over Bytes Objects

Iterating over str instances will yield individual string characters, but iterating over bytes instances will yield instances of int.

some_strings = "abc"
assert tuple(some_strings) == ("a", "b", "c")
s: str = "".join(some_strings) # iterates over "abc" and joins its elements
assert s == "abc"

some_integers = b"abc"
assert tuple(some_integers) == (97, 98, 99)
b: bytes = b"".join(some_integers)
# will raise a TypeError because elements of the iterable b"abc"
# are the integers 97, 98, 99 but bytes.join
# expects instances of bytes-like objects

StringRegex and BytesRegex are subclasses of str and bytes respectively, so they inherit this behavior. You can use a StringRegex instance as an iterable of string characters, but iterating over a BytesRegex instance will yield integers. Methods BytesRegex.concatenate and BytesRegex.join, both of which use bytes.join internally, cannot work with iterables of integers. They expect iterables of bytes-like objects.

from human_regex import BytesRegex as Bre

# as long as the iterable yields bytes-like objects, everyting is fine:
some_bytes = (b"a", Bre(b"b"), b"c")
assert Bre.concatenate(some_bytes) == Bre(b"abc")

some_integers = Bre(b"abc")
b = Bre.concatenate(some_integers) # will raise a TypeError
# because the elements of Bre(b"abc") are integers,
# rather than bytes-like objects:
assert tuple(Bre(b"abc")) == (97, 98, 99)

# we would have to convert the integers to string characters and encode them to bytes:
b = Bre.concatenate(map(lambda i: str.encode(chr(i)), some_integers))

Inherited Methods and Properties

StringRegex and BytesRegex differ slightly in their private class variables, but their public methods and properties have all been inherited from the human_regex.bases.general_regex.GeneralRegexBase class. Thus, the documentation of the StringRegex or BytesRegex's inherited public methods and properties is to be looked up there. For methods proxied from the built-in re module or inherited from str, or bytes, look in the Python's standard library documentation.