Example of interactive selector in Python

selector.py

from __future__ import annotations

import os
import shutil
import subprocess


class Selector:
    SUPPORTED_SELECTOR_COMMANDS = {"fzf", "peco"}
    ENVKEY_SELECTOR_COMMAND = "SELECTOR_COMMAND"

    def __init__(
        self,
        selector_command: str | None = None,
    ) -> None:
        self._selector_command = selector_command or self._find_selector_command()

    def __call__(self, items: list[str]) -> str:
        if self._selector_command:
            return self._select_with_command(items)
        return self._select_without_command(items)

    def _format_list(self, items: list[str]) -> str:
        return "\n".join(f"{i}: {item}" for i, item in enumerate(items, start=1))

    def _parse_result(self, line: str) -> str:
        return line.strip().split(": ", 1)[-1]

    def _select_without_command(self, items: list[str]) -> str:
        print(self._format_list(items))
        index = int(input("select index > ")) - 1
        return items[index]

    def _select_with_command(self, items: list[str]) -> str:
        assert self._selector_command is not None

        proc = subprocess.Popen(
            [self._selector_command],
            stdin=subprocess.PIPE,
            stdout=subprocess.PIPE,
            stderr=None,
        )
        stdin = proc.stdin
        stdout = proc.stdout

        assert stdin is not None
        assert stdout is not None

        stdin.write(self._format_list(items).encode())

        stdin.flush()
        stdin.close()
        proc.wait()

        return self._parse_result(stdout.read().decode())

    def _find_selector_command(self) -> str | None:
        cmd = os.environ.get(self.ENVKEY_SELECTOR_COMMAND)
        if cmd:
            return cmd
        for cmd in self.SUPPORTED_SELECTOR_COMMANDS:
            if shutil.which(cmd):
                return cmd
        return None


if __name__ == "__main__":
    selector = Selector("fzf")
    result = selector(["foo", "bar", "baz"])
    print(f"{result} was selected.")