The difference between a system language and a scripting language.

prompt.py

#!/usr/bin/env python3

# MIT License
#
# Copyright (c) 2019 rusty-snake (https://github.com/rusty-snake) <print_hello_world+License@protonmail.com>
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.

from os import listdir

def ls():
    for file in listdir():
        print(file)

def prompt():
    cmd = input("> ").strip()
    if cmd == "ls":
        ls()
    elif cmd == "exit":
        exit()

while True:
    prompt()

prompt.rs

/*
 * MIT License
 *
 * Copyright (c) 2019 rusty-snake (https://github.com/rusty-snake) <print_hello_world+License@protonmail.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 */

use std::fs;
use std::io;
use std::process::exit;

// Runing:
// install rust (https://www.rust-lang.org/tools/install)
// compile with `rustc --edition=2018 -o prompt prompt.rs
// run with `./prompt`

fn main() {
    loop {
        prompt();
    }
}

fn ls() {
    for file in fs::read_dir(".").unwrap() {
        println!("{}", file.unwrap().file_name().to_str().unwrap());
    }
}

fn prompt() {
    eprint!("> ");
    let mut cmd = String::new();
    io::stdin().read_line(&mut cmd).unwrap();
    cmd = cmd.trim().to_string();
    if cmd == "ls" {
        ls();
    } else if cmd == "exit" {
        exit(0);
    }
}