ansinout 1.0.2

A dependency-free Python library for building Terminal User Interfaces.

ANSINOUT

ANSI + IN + OUT. A small, dependency-free Python library for building Terminal User Interfaces.

Ansinout provides a thin layer over raw ANSI escape codes without the weight of a full framework.

• Zero dependencies. Only uses the standard library.
• Keyboard input utils Easy to use functions for reading user input.
• Easy styling Foreground/background colors and bold are arguments on the text primitive.
• Diff-based rendering. Only cells that have changed since the last frame are written to the terminal.

Usage

A typical program follows this lifecycle: enter VT mode, build a window, loop on input and repaint, then restore the terminal on exit.

from ansinout import (
    enable_vt_mode, exit_vt_mode,
    TuiWindow, TuiText, TermText,
    read_key, key_available, PressedKey,
    Color, BgColor,
)

fd, attrs = enable_vt_mode()
try:
    win = TuiWindow(size=(40, 10), pos=(0, 0))
    hello = win.add_text(TermText("Hello, world!", fg=Color.Cyan), pos=(0, 0))
    win.paint()

    while True:
        if key_available(0.05):
            key, raw = read_key()
            if key == PressedKey.Escape:
                break
        win.paint()
finally:
    exit_vt_mode(fd, attrs)

Screen lifecycle

enable_vt_mode() -> (fd, old_attrs)

Prepares the terminal for interactive use. The function captures the current termios attributes of standard input, switches the input file descriptor into cbreak mode so that key presses are delivered without line buffering, enters the alternate screen buffer, clears it, and moves the cursor to the home position. It returns a tuple containing the standard input file descriptor and the original termios attributes, which must be retained and passed to exit_vt_mode during shutdown.

fd, attrs = enable_vt_mode()

exit_vt_mode(fd, old_attrs)

Restores the terminal to the state it was in before enable_vt_mode was called. The function leaves the alternate screen buffer, returning the terminal to the primary screen, and restores the original termios attributes captured by enable_vt_mode. The fd and old_attrs arguments must be the values returned from that call. It should typically be invoked inside a finally block to ensure the terminal is restored regardless of how the program exits.

exit_vt_mode(fd, attrs)

TUI building blocks

TermText(value, fg=None, bg=None, bold=False)

A TermText pairs a string with an optional foreground color, an optional background color, and a bold flag. It is accepted by every TUI primitive that renders text. The styling applies uniformly to the entire string.

title = TermText("Inbox", fg=Color.White, bg=BgColor.Blue, bold=True)

TuiText

The object returned by TuiWindow.get_text. It wraps a TermText value together with an id, a position, a derived size, and a hidden flag. Instances are created by TuiWindow.add_text rather than constructed directly.

TuiWindow(size, pos)

The main container. A TuiWindow owns a grid of cells with dimensions equal to size and a list of TuiText objects positioned within it. The window itself is anchored at pos, which is interpreted as an absolute (column, row) offset in the terminal. All TuiText positions are relative to the window's anchor.

win = TuiWindow(size=(80, 24), pos=(0, 0))

add_text(value, pos) -> int

Adds a TermText to the window at the given relative (column, row) position and returns an integer id. The id is used by every other method that operates on a specific text object.

tid = win.add_text(TermText("Press Esc to quit", fg=Color.Gray), pos=(0, 23))

update_text(id, value, pos=None)

Replaces the contents and/or position of an existing text object. If value is None, the existing text is preserved and only the position is changed. If pos is None, the position is preserved. Cells previously occupied by the old text are cleared so the next paint() removes any stale characters.

win.update_text(tid, TermText("Bye!", fg=Color.Red))
win.update_text(tid, None, pos=(10, 5))
win.update_text(tid, TermText("Hi"), (0, 0))

get_text(id) -> TuiText

Returns the underlying TuiText instance for the given id or None if not found.

obj = win.get_text(tid)

hide_txt(id) and show_txt(id)

hide_txt marks the text object as hidden and clears the cells it currently occupies so the next paint erases it from the terminal. The text object and its id remain in the window and can be redisplayed with show_txt, which clears the hidden flag and rewrites the text into the grid.

win.hide_txt(tid)
win.show_txt(tid)

hide_all() and show_all()

Hide or show every text object currently in the window.

win.hide_all()
win.show_all()

remove_txt(id) and remove_all()

remove_txt clears the cells occupied by the text object and removes it from the window's text list. remove_all performs the same operation for every text object in the window.

win.remove_txt(tid)
win.remove_all()

update_position(pos)

Moves the window to a new absolute (column, row) anchor. The function hides all currently visible text objects, paints the cleared state to remove the old rendering, updates the anchor, and restores visibility at the new location.

win.update_position((5, 2))

clear_screen()

Replaces every cell in the window's grid with a space. This stages a full erase that takes effect on the next paint(). It does not remove text objects from the window.

win.clear_screen()

paint()

Flushes pending changes to the terminal. The method walks the grid and writes only the cells whose contents differ from what was last painted, then returns the cursor to the origin. Because the operation is incremental, paint() is safe to call in a tight render loop.

win.paint()

Keyboard input

key_available(timeout=0.0) -> bool

Reports whether standard input has data ready to be read. The call blocks for at most timeout seconds and returns True as soon as input becomes available, or False if the timeout elapses first. A timeout of 0.0 performs a non-blocking poll. The function is typically used in a render loop to wait briefly for input without preventing periodic repaints.

if key_available(0.05):
    key, raw = read_key()

read_key() -> (PressedKey, str)

Reads a single key press from standard input and returns a tuple of (PressedKey, raw), where PressedKey is the categorized key and raw is the underlying byte sequence as a string. The function handles multi-byte escape sequences for the arrow keys and the Delete key, and distinguishes a bare Escape press from the start of an escape sequence by waiting briefly for continuation bytes. Unknown escape sequences are reported as PressedKey.Nop with the full received sequence as the raw value.

key, raw = read_key()
if key == PressedKey.Alpha:
    buffer += raw
elif key == PressedKey.Backspace:
    buffer = buffer[:-1]

PressedKey

An enumeration of the key categories produced by read_key. The members are Alpha, ArrowUp, ArrowDown, ArrowLeft, ArrowRight, Backspace, Enter, Escape, Delete, and Nop. The Alpha category covers letters, digits, and a set of punctuation characters (_, -, ., /, \, and :). Bytes that do not match any recognized category are reported as Nop.

Cursor functions

move_cursor(row, col)

Moves the terminal cursor to the given zero-based (row, col) position without writing any text. The function is useful for placing the cursor after a series of direct writes, or for positioning a visible cursor over an input field. Errors raised while writing the escape sequence are suppressed.

move_cursor(0, 0)

change_cursor(cursor_type)

Changes the shape of the terminal cursor. The cursor_type argument is a member of the CursorTypes enumeration, which defines six shapes: Default, Blinking_Block, Steady_Block, Blinking_Underline, Steady_Underline, Blinking_Bar, and Steady_Bar. The effect persists until the next call to change_cursor or until the terminal is reset.

from ansinout.screen import CursorTypes, change_cursor
change_cursor(CursorTypes.Steady_Bar)

Direct drawing

print_pos(row, col, s, fg=None, bg=None, bold=False)

Writes the string s at the given zero-based (row, col) position. The function emits the ANSI cursor-positioning sequence followed by the styled text and flushes standard output. Coordinates are translated to the terminal's one-based addressing internally, so the caller should pass zero-based values. Styling arguments behave as on TermText: omitting fg, bg, and bold produces unstyled output.

print_pos(2, 5, "status: ok", fg=Color.Green, bold=True)

Colors

Color and BgColor

Enumerations of the sixteen standard ANSI color codes for foreground and background respectively. Each enum covers the eight base colors and their eight bright variants, along with a Default member that maps to the terminal's configured default. The two enums are kept distinct so that the type system can prevent a background color from being passed where a foreground color is expected. Values are accepted by TermText, print_pos, and any other function that takes fg or bg arguments.

TermText("warning", fg=Color.BrightYellow, bg=BgColor.Black, bold=True)

Standard colors

Name	ANSI (fg)	ANSI (bg)
Black	30	40
Red	31	41
Green	32	42
Yellow	33	43
Blue	34	44
Magenta	35	45
Cyan	36	46
White	37	47
Default	39	49

Bright colors

Name	ANSI (fg)	ANSI (bg)
BrightBlack	90	100
Gray	90	100
BrightRed	91	101
BrightGreen	92	102
BrightYellow	93	103
BrightBlue	94	104
BrightMagenta	95	105
BrightCyan	96	106
BrightWhite	97	107

Gray is an alias for BrightBlack. The exact rendering of each color is determined by the terminal's color scheme.