slTrain/sl
developtheweb 08f6ba4f69 Release 3.1.0: surprise mode and README overhaul
A bare sl now randomizes train type, coal cars, color livery, and
speed each run, with an occasional whistle (25%), rare flight (10%),
and very rare crash (5%). Any explicit flag disables the randomness
entirely, keeping all options deterministic and backward compatible.

Rewrite the README around the project's actual character: surprise
mode odds table, a how-it-works section on the renderer, and a FAQ.
Remove broken references (missing demo gif, SECURITY.md, unverified
Docker image).
2026-07-06 13:13:43 -04:00

631 lines
23 KiB
Python
Executable file

#!/usr/bin/env python3
"""
sl - Steam Locomotive
A joke command that displays an animated train when you type 'sl' instead of 'ls'
Author: Reverend Steven Milanese
License: MIT
Design notes (v3):
The entire point of sl is maximal output for minimal input -- two
mistyped letters buy you a locomotive. v3 keeps the original contract
(one file, stdlib only, same flags, Ctrl+C still works) and upgrades
the show: a flicker-free double-buffered renderer on the alternate
screen, wheels that actually turn, smoke that drifts and dissipates,
coal cars, a whistle, and a crash that earns the -a flag. When stdout
is not a terminal, a static train is printed instead of escape codes,
so `sl | cat` stays a train and not a mess.
"""
import argparse
import math
import os
import random
import signal
import sys
import time
from typing import Dict, List, Optional
# Version
__version__ = "3.1.0"
# ANSI escape codes for colors and cursor control
class ANSI:
# Colors
RED = '\033[91m'
GREEN = '\033[92m'
YELLOW = '\033[93m'
BLUE = '\033[94m'
MAGENTA = '\033[95m'
CYAN = '\033[96m'
WHITE = '\033[97m'
RESET = '\033[0m'
# Cursor and screen control
HIDE_CURSOR = '\033[?25l'
SHOW_CURSOR = '\033[?25h'
ALT_SCREEN_ON = '\033[?1049h'
ALT_SCREEN_OFF = '\033[?1049l'
BELL = '\a'
@staticmethod
def gray(level: int) -> str:
"""256-color grayscale (232 = near black .. 255 = near white)."""
return f'\033[38;5;{level}m'
@staticmethod
def move_cursor(x: int, y: int) -> str:
"""Move cursor to position (1-based)."""
return f'\033[{y};{x}H'
# Character-based coloring of the train art (original v2 palette)
CHAR_COLORS = {
'D': ANSI.RED,
'_': ANSI.YELLOW,
'|': ANSI.BLUE,
'=': ANSI.GREEN,
'O': ANSI.WHITE,
'o': ANSI.WHITE,
'~': ANSI.CYAN,
}
# Alternate liveries for surprise mode
COLOR_THEMES = [
CHAR_COLORS,
{'D': ANSI.YELLOW, '_': ANSI.RED, '|': ANSI.RED,
'=': ANSI.YELLOW, 'O': ANSI.WHITE, 'o': ANSI.WHITE, '~': ANSI.MAGENTA},
{'D': ANSI.WHITE, '_': ANSI.CYAN, '|': ANSI.BLUE,
'=': ANSI.CYAN, 'O': ANSI.WHITE, 'o': ANSI.WHITE, '~': ANSI.BLUE},
{'D': ANSI.MAGENTA, '_': ANSI.GREEN, '|': ANSI.MAGENTA,
'=': ANSI.CYAN, 'O': ANSI.YELLOW, 'o': ANSI.YELLOW, '~': ANSI.GREEN},
]
def random_theme() -> Dict[str, str]:
"""A one-off livery: each character class gets a random color."""
pool = [ANSI.RED, ANSI.GREEN, ANSI.YELLOW, ANSI.BLUE,
ANSI.MAGENTA, ANSI.CYAN, ANSI.WHITE]
return {ch: random.choice(pool) for ch in CHAR_COLORS}
class Train:
"""The ASCII art trains, their animated wheel frames, and rolling stock."""
# Classic steam locomotive
CLASSIC = [
" ==== ________ ___________",
" _D _| |_______/ \\__I_I_____===__|_________|",
" |(_)--- | H\\________/ | | =|___ ___| ",
" / | | H | | | | ||_| |_|| ",
" | | | H |__--------------------| [___] | ",
" | ________|___H__/__|_____/[][]~\\_______| | ",
" |/ | |-----------I_____I [][] [] D |=======|__",
"__/ =| o |=-~~\\ /~~\\ /~~\\ /~~\\ ____Y___________|__",
" |/-=|___|= || || || |_____/~\\___/ ",
" \\_/ \\O=====O=====O=====O_/ \\_/ "
]
# Small locomotive for narrow terminals
SMALL = [
" ++ +------ ",
" || |+-+ | ",
" /---------|| | | ",
" + ======== +-+ | ",
" _|--O========O~\\-+ ",
"//// \\_/ \\_/ "
]
# D51 locomotive (Japanese style)
D51 = [
" ==== ________ ___________ ",
" _D _| |_______/ \\__I_I_____===__|_________|",
" |(_)--- | H\\________/ | | =|___ ___| ",
" / | | H | | | | ||_| |_|| ",
" | | | H |__--------------------| [___] | ",
" | ________|___H__/__|_____/[][]~\\_______| | ",
" |/ | |-----------I_____I [][] [] D |=======|__",
"__/ =| o |=-O=====O=====O=====O \\ ____Y___________|__",
" |/-=|___|= || || || |_____/~\\___/ ",
" \\_/ \\__/ \\__/ \\__/ \\__/ \\_/ "
]
# C51 locomotive
C51 = [
" ___ ",
" _|_|_ _ __ __ ___________",
" D__/ \\_(_)___| |__H__| |_____I_Ii_()|_________|",
" | `---' |:: `--' H `--' | |___ ___| ",
" +|~~~~~~~~++::~~~~~~~H~~+=====+~~~~~~|~~||_| |_|| ",
" || | :: H +=====+ | |:: ...| ",
"| | _______|_::-----------------[][]-----| | ",
"| /~~ || |-----/~~~~\\ /[I_____I][][] --|||_______|__",
"------'|oOo|===[]- || || | ||=======_|__",
"/~\\____|___|/~\\_| O=======O=======O |__|\\ / ",
"\\_/ \\_/ \\____/ \\____/ \\____/ \\_____/ "
]
# Coal tender, adapted from Toyoda Masashi's original sl
COAL_CAR = [
" ",
" _________________ ",
" _| \\_____A ",
" =| | ",
" -| | ",
"__|________________________|_ ",
"|__________________________|_ ",
" |_D__D__D_| |_D__D__D_| ",
" \\_/ \\_/ \\_/ \\_/ ",
]
TRAINS = {
"classic": CLASSIC,
"small": SMALL,
"d51": D51,
"c51": C51,
}
# Wheel animation: (row index, pattern, 4-frame cycle). Each cycle entry
# must be the same width as the pattern it replaces.
WHEEL_SPEC = {
"classic": [
(8, "||", ["||", "//", "--", "\\\\"]),
(9, "=====", ["=====", "-====", "==-==", "===-="]),
],
"d51": [
(7, "=====", ["=====", "-====", "==-==", "===-="]),
(8, "||", ["||", "//", "--", "\\\\"]),
],
"c51": [
(9, "=======", ["=======", "-======", "===-===", "=====-="]),
],
"small": [
(4, "========", ["========", "-=======", "===-====", "=====-=="]),
],
}
# Column of the smokestack, relative to the left edge of the art
FUNNEL_X = {"classic": 7, "d51": 7, "c51": 9, "small": 5}
@classmethod
def frames(cls, style: str) -> List[List[str]]:
"""Build the wheel-animation frames for a train style."""
base = cls.TRAINS.get(style, cls.CLASSIC)
frames = []
for k in range(4):
art = list(base)
for row, pattern, cycle in cls.WHEEL_SPEC.get(style, []):
art[row] = art[row].replace(pattern, cycle[k])
frames.append(art)
return frames
@classmethod
def couple(cls, train_art: List[str], cars: int) -> List[str]:
"""Attach coal cars behind the locomotive, bottom-aligned."""
parts = [train_art] + [cls.COAL_CAR] * max(0, cars)
height = max(len(p) for p in parts)
widths = [max(len(r) for r in p) for p in parts]
rows = []
for i in range(height):
row = ""
for part, width in zip(parts, widths):
pad = height - len(part)
src = part[i - pad] if i >= pad else ""
row += src.ljust(width)
rows.append(row)
return rows
class Screen:
"""Double-buffered frame composer: draw everything into an off-screen
cell buffer, then emit the whole frame as one write. No per-frame
clear-screen means no flicker."""
def __init__(self, width: int, height: int, use_color: bool):
self.w = width
self.h = height
self.use_color = use_color
self.chars: List[List[str]] = []
self.colors: List[List[Optional[str]]] = []
self.clear()
def clear(self):
self.chars = [[' '] * self.w for _ in range(self.h)]
self.colors = [[None] * self.w for _ in range(self.h)]
def put(self, x: int, y: int, text: str,
color: Optional[str] = None,
charmap: Optional[Dict[str, str]] = None,
opaque: bool = False):
"""Draw text at (x, y), clipping to the screen. Spaces are
transparent unless opaque, in which case interior spaces (between
the first and last visible character) overwrite what's below."""
if not (0 <= y < self.h) or not text:
return
start = end = 0
if opaque:
body = text.rstrip()
start = len(body) - len(body.lstrip())
end = len(body)
row, crow = self.chars[y], self.colors[y]
for i, ch in enumerate(text):
if ch == ' ' and not (opaque and start <= i < end):
continue
cx = x + i
if 0 <= cx < self.w:
row[cx] = ch
if charmap and ch in charmap:
crow[cx] = charmap[ch]
else:
crow[cx] = color
def frame(self) -> str:
"""Serialize the buffer to a single escape-code string."""
parts = [ANSI.RESET] if self.use_color else []
current = None
for y in range(self.h):
parts.append(ANSI.move_cursor(1, y + 1))
row, crow = self.chars[y], self.colors[y]
for x in range(self.w):
if self.use_color:
color = crow[x]
if color != current:
parts.append(color if color is not None else ANSI.RESET)
current = color
parts.append(row[x])
if self.use_color and current is not None:
parts.append(ANSI.RESET)
return ''.join(parts)
class Particles:
"""Tiny particle system for smoke, crash sparks, and stardust."""
KINDS = {
# chars are indexed by age; drift/gravity give each kind its motion
"smoke": {"chars": "@@Oo*..", "gravity": 0.0, "drag": 0.98},
"spark": {"chars": "@**+x..", "gravity": 0.12, "drag": 1.0},
"stardust": {"chars": "**++...", "gravity": 0.0, "drag": 0.99},
}
def __init__(self, smoke_colors: List[str]):
self.items: List[dict] = []
self.smoke_colors = smoke_colors
def emit_smoke(self, x: float, y: float):
self.items.append({
"kind": "smoke",
"x": x + random.uniform(-1, 1), "y": y,
"vx": random.uniform(0.4, 0.9), # smoke trails behind the train
"vy": -random.uniform(0.2, 0.45),
"age": 0, "life": random.randint(14, 22),
})
def emit_spark(self, x: float, y: float):
angle = random.uniform(0, 2 * math.pi)
speed = random.uniform(0.4, 1.8)
self.items.append({
"kind": "spark",
"x": x, "y": y,
"vx": math.cos(angle) * speed,
"vy": math.sin(angle) * speed * 0.6 - 0.4,
"age": 0, "life": random.randint(10, 18),
})
def emit_stardust(self, x: float, y: float):
self.items.append({
"kind": "stardust",
"x": x, "y": y + random.uniform(-1, 1),
"vx": random.uniform(0.5, 1.1),
"vy": random.uniform(-0.15, 0.15),
"age": 0, "life": random.randint(8, 14),
})
def step(self):
alive = []
for p in self.items:
spec = self.KINDS[p["kind"]]
p["x"] += p["vx"]
p["y"] += p["vy"]
p["vx"] *= spec["drag"]
p["vy"] += spec["gravity"]
p["age"] += 1
if p["age"] < p["life"]:
alive.append(p)
self.items = alive
def draw(self, screen: Screen):
for p in self.items:
spec = self.KINDS[p["kind"]]
t = p["age"] / p["life"]
chars = spec["chars"]
ch = chars[min(int(t * len(chars)), len(chars) - 1)]
if p["kind"] == "smoke":
idx = min(int(t * len(self.smoke_colors)), len(self.smoke_colors) - 1)
color = self.smoke_colors[idx]
elif p["kind"] == "spark":
color = ANSI.WHITE if t < 0.3 else (ANSI.YELLOW if t < 0.6 else ANSI.RED)
else:
color = ANSI.CYAN if t < 0.5 else ANSI.WHITE
screen.put(int(round(p["x"])), int(round(p["y"])), ch, color=color)
class SLAnimation:
"""Main animation controller."""
def __init__(self, train_type: str = "classic", speed: float = 1.0,
fly: bool = False, accident: bool = False,
cars: int = 0, whistle: bool = False,
use_color: bool = True,
palette: Optional[Dict[str, str]] = None):
self.train_type = train_type
self.speed = max(0.1, min(speed, 20.0))
self.fly = fly
self.accident = accident
self.whistle = whistle
self.use_color = use_color
self.palette = palette or CHAR_COLORS
self.running = True
self.resized = False
base = Train.TRAINS.get(train_type, Train.CLASSIC)
self.frames = [Train.couple(f, cars) for f in Train.frames(train_type)]
self.total_w = max(len(r) for r in self.frames[0])
self.total_h = len(self.frames[0])
# If a coal car is taller than the loco, the loco is padded down
self.funnel_dy = self.total_h - len(base)
self.funnel_dx = Train.FUNNEL_X.get(train_type, 7)
self.smoke_colors, self.rail_color = self._palette()
self.update_terminal_size()
signal.signal(signal.SIGINT, self._handle_interrupt)
if hasattr(signal, 'SIGWINCH'):
signal.signal(signal.SIGWINCH, self._handle_resize)
def _palette(self):
"""Grayscale smoke on 256-color terminals, plain white elsewhere."""
term = os.environ.get('TERM', '')
if '256' in term or os.environ.get('COLORTERM'):
smoke = [ANSI.gray(g) for g in (255, 251, 248, 245, 242)]
rail = ANSI.gray(240)
else:
smoke = [ANSI.WHITE] * 5
rail = None
return smoke, rail
def update_terminal_size(self):
"""Update terminal dimensions."""
try:
size = os.get_terminal_size()
# Some ptys report 0x0; a degenerate size gets the default
self.width = size.columns if size.columns > 0 else 80
self.height = size.lines if size.lines > 0 else 24
except OSError:
self.width = 80
self.height = 24
def _handle_resize(self, signum, frame):
"""Handle terminal resize (applied at the next frame)."""
self.resized = True
def _handle_interrupt(self, signum, frame):
"""Handle Ctrl+C gracefully."""
self.running = False
@staticmethod
def _smooth(p: float) -> float:
"""Smoothstep easing for the flight path."""
return p * p * (3 - 2 * p)
def print_static(self):
"""stdout is not a terminal: print one honest train, no escapes."""
for line in self.frames[0]:
print(line.rstrip())
def run(self):
"""Run the animation."""
if not sys.stdout.isatty():
self.print_static()
return
sys.stdout.write(ANSI.ALT_SCREEN_ON + ANSI.HIDE_CURSOR)
sys.stdout.flush()
try:
self._animate()
finally:
# The alternate screen restores whatever was there before
sys.stdout.write(ANSI.SHOW_CURSOR + ANSI.ALT_SCREEN_OFF)
sys.stdout.flush()
def _animate(self):
screen = Screen(self.width, self.height, self.use_color)
particles = Particles(self.smoke_colors)
frame_dt = 0.05 / self.speed
total_frames = self.width + self.total_w + 12
toot_until = -1
toot_marks = {int(self.width * 0.66), int(self.width * 0.33)}
next_tick = time.monotonic()
frame_i = 0
while self.running and frame_i < total_frames:
if self.resized:
self.resized = False
self.update_terminal_size()
screen = Screen(self.width, self.height, self.use_color)
x = self.width - frame_i
progress = frame_i / total_frames
if self.fly:
floor_y = max(1, self.height - self.total_h - 2)
y = int(2 + (floor_y - 2) * (1 - self._smooth(progress))
+ 1.5 * math.sin(progress * 7))
y = max(1, min(self.height - self.total_h - 1, y))
else:
y = max(1, (self.height - self.total_h) // 2)
art = self.frames[(frame_i // 2) % len(self.frames)]
# Emit particles
if self.fly:
if frame_i % 2 == 0:
particles.emit_stardust(x + self.total_w, y + self.total_h - 2)
if frame_i % 2 == 0:
particles.emit_smoke(x + self.funnel_dx, y + self.funnel_dy - 1)
particles.step()
# Whistle as the funnel passes the marks
if self.whistle and (x + self.funnel_dx) in toot_marks:
sys.stdout.write(ANSI.BELL)
toot_until = frame_i + 8
# Compose the frame: rails, smoke, train, overlays
screen.clear()
if not self.fly:
screen.put(0, y + self.total_h, '-' * self.width,
color=self.rail_color)
particles.draw(screen)
for i, line in enumerate(art):
screen.put(x, y + i, line, charmap=self.palette, opaque=True)
if frame_i < toot_until:
screen.put(x + self.funnel_dx + 3, y + self.funnel_dy - 2,
'TOOT! TOOT!', color=ANSI.WHITE)
sys.stdout.write(screen.frame())
sys.stdout.flush()
# The -a flag: the train makes it halfway, and no further
if self.accident and x <= (self.width - self.total_w) // 2:
self._crash(screen, particles, x, y, art)
return
# Monotonic pacing: no drift from render time
next_tick += frame_dt
delay = next_tick - time.monotonic()
if delay > 0:
time.sleep(delay)
else:
next_tick = time.monotonic()
frame_i += 1
if x + self.total_w < 0:
break
def _crash(self, screen: Screen, particles: Particles,
x: int, y: int, art: List[str]):
"""Accident mode finale: shake, sparks, and a proper BOOM."""
messages = ['C R A S H !', 'B O O M !']
front_y = y + self.total_h // 2
for f in range(55):
if not self.running:
return
if f < 14:
for _ in range(5):
particles.emit_spark(x + random.randint(0, 8),
front_y + random.randint(-2, 2))
elif f < 40 and f % 3 == 0:
particles.emit_smoke(x + random.randint(0, 6), front_y - 2)
particles.step()
shake = f < 20
dx = random.randint(-1, 1) if shake else 0
dy = random.randint(-1, 0) if shake else 0
screen.clear()
screen.put(0, y + self.total_h, '-' * self.width,
color=self.rail_color)
particles.draw(screen)
for i, line in enumerate(art):
screen.put(x + dx, y + i + dy, line,
charmap=self.palette, opaque=True)
if f < 32 and (f // 3) % 2 == 0:
color = ANSI.RED if (f // 6) % 2 == 0 else ANSI.YELLOW
screen.put(x + 6, y - 2, messages[(f // 6) % 2], color=color)
sys.stdout.write(screen.frame())
sys.stdout.flush()
time.sleep(0.06 / self.speed)
def main():
"""Main entry point."""
parser = argparse.ArgumentParser(
prog='sl',
description='sl - Display animated steam locomotive',
epilog='A joke command for when you type sl instead of ls'
)
parser.add_argument('-a', '--accident', action='store_true',
help='an accident occurs')
parser.add_argument('-F', '--fly', action='store_true',
help='make the train fly')
parser.add_argument('-l', '--long', action='store_true',
help='use a longer train (D51 pulling coal cars)')
parser.add_argument('-c', '--C51', action='store_true',
help='use C51 train type')
parser.add_argument('-t', '--type', choices=sorted(Train.TRAINS),
help='locomotive type (overrides -l/-c)')
parser.add_argument('-n', '--cars', type=int, default=0, metavar='N',
help='number of coal cars to pull (default: 0)')
parser.add_argument('-w', '--whistle', action='store_true',
help='sound the whistle as the train passes')
parser.add_argument('-s', '--speed', type=float, default=1.0,
help='animation speed multiplier (default: 1.0)')
parser.add_argument('--no-color', action='store_true',
help='disable colors (NO_COLOR is also honored)')
parser.add_argument('-v', '--version', action='version',
version=f'sl version {__version__}')
args = parser.parse_args()
# Determine train type
if args.type:
train_type = args.type
elif args.C51:
train_type = "c51"
elif args.long:
train_type = "d51"
else:
train_type = "classic"
cars = max(0, min(args.cars, 8))
if args.long and args.cars == 0:
cars = 2 # --long should actually be long
use_color = (not args.no_color
and 'NO_COLOR' not in os.environ
and sys.stdout.isatty())
# Surprise mode: a bare `sl` -- the classic mistyped `ls` -- rolls the
# dice on everything, so no two typos look alike. Any flag at all
# switches back to fully deterministic behavior.
palette = None
speed = args.speed
fly, accident, whistle = args.fly, args.accident, args.whistle
if len(sys.argv) == 1:
train_type = random.choice(list(Train.TRAINS))
cars = random.choice([0, 0, 0, 1, 2, 2, 3, 4, 8])
palette = random.choice(COLOR_THEMES + [random_theme()])
speed = random.uniform(0.8, 1.5)
whistle = random.random() < 0.25
roll = random.random()
accident = roll < 0.05 # rare: the typo ends in tragedy
fly = 0.05 <= roll < 0.15 # rare: the typo takes flight
# Run animation
animation = SLAnimation(
train_type=train_type,
speed=speed,
fly=fly,
accident=accident,
cars=cars,
whistle=whistle,
use_color=use_color,
palette=palette,
)
animation.run()
if __name__ == "__main__":
main()