Tetanus esolang

tetanus.py

import regex as re
import sys

# Please let me know about any bugs! I can be reached at Yanqui#2401 on Discord

# Last argument is program filename

prog_filename = sys.argv[-1]

with open(prog_filename) as f:
    lines = f.read().split("\n")
    pattern = re.compile(lines[0])
    replacement = lines[1]

    if len(lines) > 2:
        data = "\n".join(lines[2:])
    else:
        data = ""

special_groups = {"output": [], "input": []}

ops = ["~", "`"]

not_escaped_lookbehind = r"(?<!(?<!\\)\\(?:\\\\)*)"
group_pattern = r"(?|\\(\d+)|\\g<([^>]+)>)"
op_pattern = r"(~`|`~|[~`])"
for group, op in re.findall(
        rf"{not_escaped_lookbehind}{group_pattern}{op_pattern}", replacement):

    if group.isdigit():
        group = int(group)

    if "~" in op:
        special_groups["output"].append(group)

    if "`" in op:
        special_groups["input"].append(group)

replacement = re.sub(
    rf"{not_escaped_lookbehind}({group_pattern}){op_pattern}", r"\1", replacement
)

while True:
    search = pattern.search(data)

    if search:
        data = pattern.sub(replacement, data)

        for g in special_groups["output"]:
            captured_text = search.group(g)
            if captured_text:
                print(captured_text, end="")

        for g in special_groups["input"]:
            if search.group(g):
                data += input()
    else:
        break

tetanus