mckirk / aocparser

aocparser

This package is a simple parser for puzzle inputs such as the Advent of Code input files.

Grammar

The grammar consists of four basic constructs:

Literals

Literals are matched exactly. Characters with special meaning, i.e. [, ], {, }, <, >, and | must be escaped with a backtick (`).

foo`|bar matches foo|bar.

Value elements

Value elements (i.e., elements that should be parsed into a value) are denoted by curly brackets ({ and }), with the type given after a colon (:):

{foo:i} matches 42 and parses into {'foo': 42}.

The name of the value element is optional. If no name is given, the value is stored with its index as its key. If none of the value elements in the container element are named, the container element is parsed into a list. Otherwise, it is parsed into a dict.

{i}{i} matches 42 43 and parses into [42, 43]

{i}{bar:i} matches 42 43 and parses into {0: 42, 'bar': 43}.

Defined types

Currently, the following types are defined:

• i: integer
• w: word (i.e., an alphanumeric string without whitespace)
• n: name (i.e., a word not starting with a number)
• il: list of integers
• wl: list of words
• nl: list of names

Container elements

Container elements (i.e., elements that should be parsed into a list or a dict) are denoted by square brackets ([ and ]), with the 'join string' given after a pipe (|):

[{i}|,] matches 42,43 and parses into [42, 43].

The join string is optional. If no join string is given, it will default to (an arbitrary amount of) spaces.

[{i}] matches 42 43 and parses into [42, 43].

Dicts

If a value element inside the container has the name key, the container is parsed into a dict, with the value of the key element as the key.

[{key:w} = {val:i}|\n] matches

foo = 42
bar = 43

and parses into

{'foo': {'key': 'foo', 'val': 42},
 'bar': {'key': 'bar', 'val': 43}}

If a container has two child elements, one 'key' element and one unnamed element, the unnamed element gets returned directly as the value:

[{key:w} = {i}|\n] matches

foo = 42
bar = 43

and parses into

{'foo': 42,
 'bar': 43}

Choice elements

Choice elements (i.e., elements that should be parsed into one of multiple options) are denoted by angle brackets (< and >), with the choices separated by a pipe (|). To distinguish the choices, they need to be named, with the name given before a colon (:).

<num:{i}|word:{w}|nop:nop> matches 42 and parses into dict(num=42, word=None), and matches foo and parses into dict(word='foo', num=None).

If all choices contain an element with the same name, that element is lifted to the result of the choice element as well.

<inc:{n:w}++|dec:{n:w}--> matches a++ and parses into dict(n='a', inc={'n': 'a'}, dec=None), and matches a-- and parses into dict(n='a', dec={'n': 'a'}, inc=None).

Returned 'dict' type

The returned dictionaries are actually NamespaceDicts, which subclass dictionaries to also allow access to the values as attributes. This means that parsed['foo'] is equivalent to parsed.foo.

Examples

2023/day04

from aocparser import parse

example = """\
Card 1: 41 48 83 86 17 | 83 86  6 31 17  9 48 53
Card 2: 13 32 20 16 61 | 61 30 68 82 17 32 24 19"""

spec = "[Card {key:i}: {p1:il} `| {p2:il}|\n]"

assert parse(spec, example) == {
    1: {"key": 1,
        "p1": [41, 48, 83, 86, 17],
        "p2": [83, 86, 6, 31, 17, 9, 48, 53]},
    2: {
        "key": 2,
        "p1": [13, 32, 20, 16, 61],
        "p2": [61, 30, 68, 82, 17, 32, 24, 19],
    },
}

2023/day05

from aocparser import parse

example = """\
seeds: 79 14 55 13

seed-to-soil map:
50 98 2
52 50 48"""

spec = """\
seeds: {seeds:il}

{maps:[{key:w}-to-{to:w} map:
{vals:[{il}|\n]}|\n\n]}"""

assert parse(spec, example) == {
    "maps": {
        "seed": {"key": "seed", "to": "soil", "vals": [[50, 98, 2], [52, 50, 48]]}
    },
    "seeds": [79, 14, 55, 13],
}

2023/day08

from aocparser import parse

example = """\
RL

AAA = (BBB, CCC)
BBB = (DDD, EEE)"""

spec = """\
{w}

[{key:w} = ({L:w}, {R:w})|\n]"""

assert parse(spec, example) == [
    "RL",
    {
        "AAA": {"L": "BBB", "R": "CCC", "key": "AAA"},
        "BBB": {"L": "DDD", "R": "EEE", "key": "BBB"},
    },
]

2020/day14

from aocparser import parse

example = """\
mask = 00
mem[1] = 1
mask = 01
mem[2] = 2"""

spec = "[<mask:mask = {w}|mem:mem`[{i}`] = {i}>|\n]"

assert parsed == [
    {"mask": "00", "mem": None},
    {"mask": None, "mem": {"addr": 1, "val": 1}},
    {"mask": "01", "mem": None},
    {"mask": None, "mem": {"addr": 2, "val": 2}},
]

assert parsed[0].mask == "00"
assert parsed[1].mem.addr == 1

2023/day15

from aocparser import parse

example = "a=1,b=2,c-"

spec = "[<set:{n:w}={v:i}|minus:{n:w}->|,]"

parsed = parse(spec, example)

assert parsed == [
    {"minus": None, "n": "a", "set": {"n": "a", "v": 1}},
    {"minus": None, "n": "b", "set": {"n": "b", "v": 2}},
    {"minus": {"n": "c"}, "n": "c", "set": None},
]

assert parsed[0].n == "a"
assert parsed[2].n == "c"