┌──────────────────────────────────────────────────┐
   │  c o d e c h u — t e r m                         │
   │  $ _                                             │
   │  ····TTY detection · alt buffer · raw mode······ │
   └──────────────────────────────────────────────────┘

Terminal capability detection and low-level control, stdlib-only.

codechu-term

Stdlib-only terminal-capability detection and low-level terminal control — extracted from the codechu/cli-py private _term module and expanded with the bits Codechu CLIs actually use. No external dependencies. Python 3.10+, POSIX-first.

Install

pip install codechu-term

API

import os, sys
from codechu_term import (
    is_tty, terminal_size, capabilities,
    with_alt_buffer, with_raw_mode, on_resize,
    hide_cursor, show_cursor, clear_line, clear_screen,
)

is_tty(sys.stderr)                          # → True / False

terminal_size()                             # → (cols, rows), e.g. (120, 40)
terminal_size(env={"COLUMNS": "100", "LINES": "30"})  # explicit env

capabilities(sys.stdout, env=os.environ)
# → {'color': True, 'truecolor': True, 'unicode': True,
#    'emoji': True, 'mouse': True, 'alt_buffer': True}

with with_alt_buffer() as out:              # full-screen mode
    out.write("hello, alt buffer\n"); out.flush()

with with_raw_mode() as fd:                 # char-by-char input
    ch = os.read(fd, 1)

remove = on_resize(lambda: print("resized!"))
# ... later
remove()

hide_cursor(); show_cursor()
clear_line(); clear_screen()

is_tty(stream)

Defensive isatty() — accepts None and any object, swallows exceptions, returns False for anything that isn't a confirmed TTY.

terminal_size(stream=sys.stderr, *, env=None)

Resolution ladder:

1. os.get_terminal_size(stream.fileno()) when available.
2. COLUMNS / LINES from env (defaults to os.environ).
3. (80, 24) as a final fallback.

Never raises.

capabilities(stream, env=None)

Returns six boolean flags:

env is taken explicitly — pass env=os.environ for the live process environment.

with_alt_buffer(stream=sys.stdout)

Context manager that switches to the alt screen buffer (\x1b[?1049h) on entry and restores the main buffer (\x1b[?1049l) on exit — even when the block raises.

with_raw_mode(fd=sys.stdin.fileno())

termios/tty raw mode for char-by-char input. Restores the original terminal attributes in a finally block, so the terminal never gets stuck. POSIX only.

on_resize(callback)

Installs callback as a SIGWINCH handler and returns a remover function that restores the previous handler. The callback is invoked with no arguments. POSIX only.

hide_cursor() / show_cursor() / clear_line() / clear_screen()

Best-effort emitters for the corresponding ANSI sequences (\x1b[?25l, \x1b[?25h, \x1b[2K\r, \x1b[2J\x1b[H). They never raise — a closed stream is silently ignored.

Design

• Pure stdlib. Zero third-party dependencies.
• Explicit env. Capability detection never reads os.environ implicitly — the caller passes the dict. Makes testing trivial and avoids surprises in nested processes.
• Defensive. Helpers tolerate None streams, closed streams, and missing methods. They never raise from a "best-effort" path.
• POSIX-first. with_raw_mode and on_resize are POSIX-only (termios / SIGWINCH); they raise OSError on Windows rather than silently no-op.

Tests

pip install -e ".[dev]"
pytest -q

Tests that require a real TTY (raw mode, SIGWINCH propagation) skip themselves when running headless.

License

MIT — see LICENSE.