:mod:`curses` --- Terminal handling for character-cell displays

.. module:: curses
 :synopsis: An interface to the curses library, providing portable
 terminal handling.
 :platform: Unix

.. sectionauthor:: Moshe Zadka <moshez@zadka.site.co.il>

.. sectionauthor:: Eric Raymond <esr@thyrsus.com>

The :mod:`curses` module provides an interface to the curses library, the de-facto standard for portable advanced terminal handling.

While curses is most widely used in the Unix environment, versions are available for Windows, DOS, and possibly other systems as well. This extension module is designed to match the API of ncurses, an open-source curses library hosted on Linux and the BSD variants of Unix.

import locale
locale.setlocale(locale.LC_ALL, '')
code = locale.getpreferredencoding()

.. seealso::

 Module :mod:`curses.ascii`
 Utilities for working with ASCII characters, regardless of your locale settings.

 Module :mod:`curses.panel`
 A panel stack extension that adds depth to curses windows.

 Module :mod:`curses.textpad`
 Editable text widget for curses supporting :program:`Emacs`\ -like bindings.

 :ref:`curses-howto`
 Tutorial material on using curses with Python, by Andrew Kuchling and Eric
 Raymond.

 The :source:`Tools/demo/` directory in the Python source distribution contains
 some example programs using the curses bindings provided by this module.

Functions

The module :mod:`curses` defines the following exception:

.. exception:: error

 Exception raised when a curses library function returns an error.

The module :mod:`curses` defines the following functions:

.. function:: baudrate()

 Return the output speed of the terminal in bits per second. On software
 terminal emulators it will have a fixed high value. Included for historical
 reasons; in former times, it was used to write output loops for time delays and
 occasionally to change interfaces depending on the line speed.

.. function:: beep()

 Emit a short attention sound.

.. function:: can_change_color()

 Return ``True`` or ``False``, depending on whether the programmer can change the colors
 displayed by the terminal.

.. function:: cbreak()

 Enter cbreak mode. In cbreak mode (sometimes called "rare" mode) normal tty
 line buffering is turned off and characters are available to be read one by one.
 However, unlike raw mode, special characters (interrupt, quit, suspend, and flow
 control) retain their effects on the tty driver and calling program. Calling
 first :func:`raw` then :func:`cbreak` leaves the terminal in cbreak mode.

.. function:: color_content(color_number)

 Return the intensity of the red, green, and blue (RGB) components in the color
 *color_number*, which must be between ``0`` and :const:`COLORS`. Return a 3-tuple,
 containing the R,G,B values for the given color, which will be between
 ``0`` (no component) and ``1000`` (maximum amount of component).

.. function:: color_pair(color_number)

 Return the attribute value for displaying text in the specified color. This
 attribute value can be combined with :const:`A_STANDOUT`, :const:`A_REVERSE`,
 and the other :const:`A_\*` attributes. :func:`pair_number` is the counterpart
 to this function.

.. function:: curs_set(visibility)

 Set the cursor state. *visibility* can be set to ``0``, ``1``, or ``2``, for invisible,
 normal, or very visible. If the terminal supports the visibility requested, return the
 previous cursor state; otherwise raise an exception. On many
 terminals, the "visible" mode is an underline cursor and the "very visible" mode
 is a block cursor.

.. function:: def_prog_mode()

 Save the current terminal mode as the "program" mode, the mode when the running
 program is using curses. (Its counterpart is the "shell" mode, for when the
 program is not in curses.) Subsequent calls to :func:`reset_prog_mode` will
 restore this mode.

.. function:: def_shell_mode()

 Save the current terminal mode as the "shell" mode, the mode when the running
 program is not using curses. (Its counterpart is the "program" mode, when the
 program is using curses capabilities.) Subsequent calls to
 :func:`reset_shell_mode` will restore this mode.

.. function:: delay_output(ms)

 Insert an *ms* millisecond pause in output.

.. function:: doupdate()

 Update the physical screen. The curses library keeps two data structures, one
 representing the current physical screen contents and a virtual screen
 representing the desired next state. The :func:`doupdate` ground updates the
 physical screen to match the virtual screen.

 The virtual screen may be updated by a :meth:`~window.noutrefresh` call after write
 operations such as :meth:`~window.addstr` have been performed on a window. The normal
 :meth:`~window.refresh` call is simply :meth:`!noutrefresh` followed by :func:`!doupdate`;
 if you have to update multiple windows, you can speed performance and perhaps
 reduce screen flicker by issuing :meth:`!noutrefresh` calls on all windows,
 followed by a single :func:`!doupdate`.

.. function:: echo()

 Enter echo mode. In echo mode, each character input is echoed to the screen as
 it is entered.

.. function:: endwin()

 De-initialize the library, and return terminal to normal status.

.. function:: erasechar()

 Return the user's current erase character as a one-byte bytes object. Under Unix operating systems this
 is a property of the controlling tty of the curses program, and is not set by
 the curses library itself.

.. function:: filter()

 The :func:`.filter` routine, if used, must be called before :func:`initscr` is
 called. The effect is that, during those calls, :envvar:`LINES` is set to ``1``; the
 capabilities ``clear``, ``cup``, ``cud``, ``cud1``, ``cuu1``, ``cuu``, ``vpa`` are disabled; and the ``home``
 string is set to the value of ``cr``. The effect is that the cursor is confined to
 the current line, and so are screen updates. This may be used for enabling
 character-at-a-time line editing without touching the rest of the screen.

.. function:: flash()

 Flash the screen. That is, change it to reverse-video and then change it back
 in a short interval. Some people prefer such as 'visible bell' to the audible
 attention signal produced by :func:`beep`.

.. function:: flushinp()

 Flush all input buffers. This throws away any typeahead that has been typed
 by the user and has not yet been processed by the program.

.. function:: getmouse()

 After :meth:`~window.getch` returns :const:`KEY_MOUSE` to signal a mouse event, this
 method should be call to retrieve the queued mouse event, represented as a
 5-tuple ``(id, x, y, z, bstate)``. *id* is an ID value used to distinguish
 multiple devices, and *x*, *y*, *z* are the event's coordinates. (*z* is
 currently unused.) *bstate* is an integer value whose bits will be set to
 indicate the type of event, and will be the bitwise OR of one or more of the
 following constants, where *n* is the button number from 1 to 4:
 :const:`BUTTONn_PRESSED`, :const:`BUTTONn_RELEASED`, :const:`BUTTONn_CLICKED`,
 :const:`BUTTONn_DOUBLE_CLICKED`, :const:`BUTTONn_TRIPLE_CLICKED`,
 :const:`BUTTON_SHIFT`, :const:`BUTTON_CTRL`, :const:`BUTTON_ALT`.

.. function:: getsyx()

 Return the current coordinates of the virtual screen cursor as a tuple
 ``(y, x)``. If :meth:`leaveok <window.leaveok>` is currently ``True``, then return ``(-1, -1)``.

.. function:: getwin(file)

 Read window related data stored in the file by an earlier :func:`putwin` call.
 The routine then creates and initializes a new window using that data, returning
 the new window object.

.. function:: has_colors()

 Return ``True`` if the terminal can display colors; otherwise, return ``False``.

.. function:: has_ic()

 Return ``True`` if the terminal has insert- and delete-character capabilities.
 This function is included for historical reasons only, as all modern software
 terminal emulators have such capabilities.

.. function:: has_il()

 Return ``True`` if the terminal has insert- and delete-line capabilities, or can
 simulate them using scrolling regions. This function is included for
 historical reasons only, as all modern software terminal emulators have such
 capabilities.

.. function:: has_key(ch)

 Take a key value *ch*, and return ``True`` if the current terminal type recognizes
 a key with that value.

.. function:: halfdelay(tenths)

 Used for half-delay mode, which is similar to cbreak mode in that characters
 typed by the user are immediately available to the program. However, after
 blocking for *tenths* tenths of seconds, raise an exception if nothing has
 been typed. The value of *tenths* must be a number between ``1`` and ``255``. Use
 :func:`nocbreak` to leave half-delay mode.

.. function:: init_color(color_number, r, g, b)

 Change the definition of a color, taking the number of the color to be changed
 followed by three RGB values (for the amounts of red, green, and blue
 components). The value of *color_number* must be between ``0`` and
 :const:`COLORS`. Each of *r*, *g*, *b*, must be a value between ``0`` and
 ``1000``. When :func:`init_color` is used, all occurrences of that color on the
 screen immediately change to the new definition. This function is a no-op on
 most terminals; it is active only if :func:`can_change_color` returns ``True``.

.. function:: init_pair(pair_number, fg, bg)

 Change the definition of a color-pair. It takes three arguments: the number of
 the color-pair to be changed, the foreground color number, and the background
 color number. The value of *pair_number* must be between ``1`` and
 ``COLOR_PAIRS - 1`` (the ``0`` color pair is wired to white on black and cannot
 be changed). The value of *fg* and *bg* arguments must be between ``0`` and
 :const:`COLORS`. If the color-pair was previously initialized, the screen is
 refreshed and all occurrences of that color-pair are changed to the new
 definition.

.. function:: initscr()

 Initialize the library. Return a :ref:`window <curses-window-objects>` object
 which represents the whole screen.

 .. note::

 If there is an error opening the terminal, the underlying curses library may
 cause the interpreter to exit.

.. function:: is_term_resized(nlines, ncols)

 Return ``True`` if :func:`resize_term` would modify the window structure,
 ``False`` otherwise.

.. function:: isendwin()

 Return ``True`` if :func:`endwin` has been called (that is, the curses library has
 been deinitialized).

.. function:: keyname(k)

 Return the name of the key numbered *k* as a bytes object. The name of a key generating printable
 ASCII character is the key's character. The name of a control-key combination
 is a two-byte bytes object consisting of a caret (``b'^'``) followed by the corresponding
 printable ASCII character. The name of an alt-key combination (128--255) is a
 bytes object consisting of the prefix ``b'M-'`` followed by the name of the corresponding
 ASCII character.

.. function:: killchar()

 Return the user's current line kill character as a one-byte bytes object. Under Unix operating systems
 this is a property of the controlling tty of the curses program, and is not set
 by the curses library itself.

.. function:: longname()

 Return a bytes object containing the terminfo long name field describing the current
 terminal. The maximum length of a verbose description is 128 characters. It is
 defined only after the call to :func:`initscr`.

.. function:: meta(flag)

 If *flag* is ``True``, allow 8-bit characters to be input. If
 *flag* is ``False``, allow only 7-bit chars.

.. function:: mouseinterval(interval)

 Set the maximum time in milliseconds that can elapse between press and release
 events in order for them to be recognized as a click, and return the previous
 interval value. The default value is 200 msec, or one fifth of a second.

.. function:: mousemask(mousemask)

 Set the mouse events to be reported, and return a tuple ``(availmask,
 oldmask)``. *availmask* indicates which of the specified mouse events can be
 reported; on complete failure it returns ``0``. *oldmask* is the previous value of
 the given window's mouse event mask. If this function is never called, no mouse
 events are ever reported.

.. function:: napms(ms)

 Sleep for *ms* milliseconds.

.. function:: newpad(nlines, ncols)

 Create and return a pointer to a new pad data structure with the given number
 of lines and columns. Return a pad as a window object.

 A pad is like a window, except that it is not restricted by the screen size, and
 is not necessarily associated with a particular part of the screen. Pads can be
 used when a large window is needed, and only a part of the window will be on the
 screen at one time. Automatic refreshes of pads (such as from scrolling or
 echoing of input) do not occur. The :meth:`~window.refresh` and :meth:`~window.noutrefresh`
 methods of a pad require 6 arguments to specify the part of the pad to be
 displayed and the location on the screen to be used for the display. The
 arguments are *pminrow*, *pmincol*, *sminrow*, *smincol*, *smaxrow*, *smaxcol*; the *p*
 arguments refer to the upper left corner of the pad region to be displayed and
 the *s* arguments define a clipping box on the screen within which the pad region
 is to be displayed.

.. function:: newwin(nlines, ncols)
 newwin(nlines, ncols, begin_y, begin_x)

 Return a new :ref:`window <curses-window-objects>`, whose left-upper corner
 is at ``(begin_y, begin_x)``, and whose height/width is *nlines*/*ncols*.

 By default, the window will extend from the specified position to the lower
 right corner of the screen.

.. function:: nl()

 Enter newline mode. This mode translates the return key into newline on input,
 and translates newline into return and line-feed on output. Newline mode is
 initially on.

.. function:: nocbreak()

 Leave cbreak mode. Return to normal "cooked" mode with line buffering.

.. function:: noecho()

 Leave echo mode. Echoing of input characters is turned off.

.. function:: nonl()

 Leave newline mode. Disable translation of return into newline on input, and
 disable low-level translation of newline into newline/return on output (but this
 does not change the behavior of ``addch('\n')``, which always does the
 equivalent of return and line feed on the virtual screen). With translation
 off, curses can sometimes speed up vertical motion a little; also, it will be
 able to detect the return key on input.

.. function:: noqiflush()

 When the :func:`!noqiflush` routine is used, normal flush of input and output queues
 associated with the ``INTR``, ``QUIT`` and ``SUSP`` characters will not be done. You may
 want to call :func:`!noqiflush` in a signal handler if you want output to
 continue as though the interrupt had not occurred, after the handler exits.

.. function:: noraw()

 Leave raw mode. Return to normal "cooked" mode with line buffering.

.. function:: pair_content(pair_number)

 Return a tuple ``(fg, bg)`` containing the colors for the requested color pair.
 The value of *pair_number* must be between ``1`` and ``COLOR_PAIRS - 1``.

.. function:: pair_number(attr)

 Return the number of the color-pair set by the attribute value *attr*.
 :func:`color_pair` is the counterpart to this function.

.. function:: putp(str)

 Equivalent to ``tputs(str, 1, putchar)``; emit the value of a specified
 terminfo capability for the current terminal. Note that the output of :func:`putp`
 always goes to standard output.

.. function:: qiflush([flag])

 If *flag* is ``False``, the effect is the same as calling :func:`noqiflush`. If
 *flag* is ``True``, or no argument is provided, the queues will be flushed when
 these control characters are read.

.. function:: raw()

 Enter raw mode. In raw mode, normal line buffering and processing of
 interrupt, quit, suspend, and flow control keys are turned off; characters are
 presented to curses input functions one by one.

.. function:: reset_prog_mode()

 Restore the terminal to "program" mode, as previously saved by
 :func:`def_prog_mode`.

.. function:: reset_shell_mode()

 Restore the terminal to "shell" mode, as previously saved by
 :func:`def_shell_mode`.

.. function:: resetty()

 Restore the state of the terminal modes to what it was at the last call to
 :func:`savetty`.

.. function:: resize_term(nlines, ncols)

 Backend function used by :func:`resizeterm`, performing most of the work;
 when resizing the windows, :func:`resize_term` blank-fills the areas that are
 extended. The calling application should fill in these areas with
 appropriate data. The :func:`!resize_term` function attempts to resize all
 windows. However, due to the calling convention of pads, it is not possible
 to resize these without additional interaction with the application.

.. function:: resizeterm(nlines, ncols)

 Resize the standard and current windows to the specified dimensions, and
 adjusts other bookkeeping data used by the curses library that record the
 window dimensions (in particular the SIGWINCH handler).

.. function:: savetty()

 Save the current state of the terminal modes in a buffer, usable by
 :func:`resetty`.

.. function:: setsyx(y, x)

 Set the virtual screen cursor to *y*, *x*. If *y* and *x* are both ``-1``, then
 :meth:`leaveok <window.leaveok>` is set ``True``.

.. function:: setupterm(term=None, fd=-1)

 Initialize the terminal. *term* is a string giving
 the terminal name, or ``None``; if omitted or ``None``, the value of the
 :envvar:`TERM` environment variable will be used. *fd* is the
 file descriptor to which any initialization sequences will be sent; if not
 supplied or ``-1``, the file descriptor for ``sys.stdout`` will be used.

.. function:: start_color()

 Must be called if the programmer wants to use colors, and before any other color
 manipulation routine is called. It is good practice to call this routine right
 after :func:`initscr`.

 :func:`start_color` initializes eight basic colors (black, red, green, yellow,
 blue, magenta, cyan, and white), and two global variables in the :mod:`curses`
 module, :const:`COLORS` and :const:`COLOR_PAIRS`, containing the maximum number
 of colors and color-pairs the terminal can support. It also restores the colors
 on the terminal to the values they had when the terminal was just turned on.

.. function:: termattrs()

 Return a logical OR of all video attributes supported by the terminal. This
 information is useful when a curses program needs complete control over the
 appearance of the screen.

.. function:: termname()

 Return the value of the environment variable :envvar:`TERM`, as a bytes object,
 truncated to 14 characters.

.. function:: tigetflag(capname)

 Return the value of the Boolean capability corresponding to the terminfo
 capability name *capname* as an integer. Return the value ``-1`` if *capname* is not a
 Boolean capability, or ``0`` if it is canceled or absent from the terminal
 description.

.. function:: tigetnum(capname)

 Return the value of the numeric capability corresponding to the terminfo
 capability name *capname* as an integer. Return the value ``-2`` if *capname* is not a
 numeric capability, or ``-1`` if it is canceled or absent from the terminal
 description.

.. function:: tigetstr(capname)

 Return the value of the string capability corresponding to the terminfo
 capability name *capname* as a bytes object. Return ``None`` if *capname*
 is not a terminfo "string capability", or is canceled or absent from the
 terminal description.

.. function:: tparm(str[, ...])

 Instantiate the bytes object *str* with the supplied parameters, where *str* should
 be a parameterized string obtained from the terminfo database. E.g.
 ``tparm(tigetstr("cup"), 5, 3)`` could result in ``b'033円[6;4H'``, the exact
 result depending on terminal type.

.. function:: typeahead(fd)

 Specify that the file descriptor *fd* be used for typeahead checking. If *fd*
 is ``-1``, then no typeahead checking is done.

 The curses library does "line-breakout optimization" by looking for typeahead
 periodically while updating the screen. If input is found, and it is coming
 from a tty, the current update is postponed until refresh or doupdate is called
 again, allowing faster response to commands typed in advance. This function
 allows specifying a different file descriptor for typeahead checking.

.. function:: unctrl(ch)

 Return a bytes object which is a printable representation of the character *ch*.
 Control characters are represented as a caret followed by the character, for
 example as ``b'^C'``. Printing characters are left as they are.

.. function:: ungetch(ch)

 Push *ch* so the next :meth:`~window.getch` will return it.

 .. note::

 Only one *ch* can be pushed before :meth:`!getch` is called.

.. function:: update_lines_cols()

 Update :envvar:`LINES` and :envvar:`COLS`. Useful for detecting manual screen resize.

 .. versionadded:: 3.5

.. function:: unget_wch(ch)

 Push *ch* so the next :meth:`~window.get_wch` will return it.

 .. note::

 Only one *ch* can be pushed before :meth:`!get_wch` is called.

 .. versionadded:: 3.3

.. function:: ungetmouse(id, x, y, z, bstate)

 Push a :const:`KEY_MOUSE` event onto the input queue, associating the given
 state data with it.

.. function:: use_env(flag)

 If used, this function should be called before :func:`initscr` or newterm are
 called. When *flag* is ``False``, the values of lines and columns specified in the
 terminfo database will be used, even if environment variables :envvar:`LINES`
 and :envvar:`COLUMNS` (used by default) are set, or if curses is running in a
 window (in which case default behavior would be to use the window size if
 :envvar:`LINES` and :envvar:`COLUMNS` are not set).

.. function:: use_default_colors()

 Allow use of default values for colors on terminals supporting this feature. Use
 this to support transparency in your application. The default color is assigned
 to the color number ``-1``. After calling this function, ``init_pair(x,
 curses.COLOR_RED, -1)`` initializes, for instance, color pair *x* to a red
 foreground color on the default background.

.. function:: wrapper(func, ...)

 Initialize curses and call another callable object, *func*, which should be the
 rest of your curses-using application. If the application raises an exception,
 this function will restore the terminal to a sane state before re-raising the
 exception and generating a traceback. The callable object *func* is then passed
 the main window 'stdscr' as its first argument, followed by any other arguments
 passed to :func:`!wrapper`. Before calling *func*, :func:`!wrapper` turns on
 cbreak mode, turns off echo, enables the terminal keypad, and initializes colors
 if the terminal has color support. On exit (whether normally or by exception)
 it restores cooked mode, turns on echo, and disables the terminal keypad.

Window Objects

Window objects, as returned by :func:`initscr` and :func:`newwin` above, have the following methods and attributes:

.. method:: window.addch(ch[, attr])
 window.addch(y, x, ch[, attr])

 Paint character *ch* at ``(y, x)`` with attributes *attr*, overwriting any
 character previously painter at that location. By default, the character
 position and attributes are the current settings for the window object.

 .. note::

 Writing outside the window, subwindow, or pad raises a :exc:`curses.error`.
 Attempting to write to the lower right corner of a window, subwindow,
 or pad will cause an exception to be raised after the character is printed.

.. method:: window.addnstr(str, n[, attr])
 window.addnstr(y, x, str, n[, attr])

 Paint at most *n* characters of the character string *str* at
 ``(y, x)`` with attributes
 *attr*, overwriting anything previously on the display.

.. method:: window.addstr(str[, attr])
 window.addstr(y, x, str[, attr])

 Paint the character string *str* at ``(y, x)`` with attributes
 *attr*, overwriting anything previously on the display.

 .. note::

 * Writing outside the window, subwindow, or pad raises :exc:`curses.error`.
 Attempting to write to the lower right corner of a window, subwindow,
 or pad will cause an exception to be raised after the string is printed.

 * A `bug in ncurses <https://bugs.python.org/issue35924>`_, the backend
 for this Python module, can cause SegFaults when resizing windows. This
 is fixed in ncurses-6.1-20190511. If you are stuck with an earlier
 ncurses, you can avoid triggering this if you do not call :func:`addstr`
 with a *str* that has embedded newlines. Instead, call :func:`addstr`
 separately for each line.

.. method:: window.attroff(attr)

 Remove attribute *attr* from the "background" set applied to all writes to the
 current window.

.. method:: window.attron(attr)

 Add attribute *attr* from the "background" set applied to all writes to the
 current window.

.. method:: window.attrset(attr)

 Set the "background" set of attributes to *attr*. This set is initially
 ``0`` (no attributes).

.. method:: window.bkgd(ch[, attr])

 Set the background property of the window to the character *ch*, with
 attributes *attr*. The change is then applied to every character position in
 that window:

 * The attribute of every character in the window is changed to the new
 background attribute.

 * Wherever the former background character appears, it is changed to the new
 background character.

.. method:: window.bkgdset(ch[, attr])

 Set the window's background. A window's background consists of a character and
 any combination of attributes. The attribute part of the background is combined
 (OR'ed) with all non-blank characters that are written into the window. Both
 the character and attribute parts of the background are combined with the blank
 characters. The background becomes a property of the character and moves with
 the character through any scrolling and insert/delete line/character operations.

.. method:: window.border([ls[, rs[, ts[, bs[, tl[, tr[, bl[, br]]]]]]]])

 Draw a border around the edges of the window. Each parameter specifies the
 character to use for a specific part of the border; see the table below for more
 details.

 .. note::

 A ``0`` value for any parameter will cause the default character to be used for
 that parameter. Keyword parameters can *not* be used. The defaults are listed
 in this table:

 +-----------+---------------------+-----------------------+
 | Parameter | Description | Default value |
 +===========+=====================+=======================+
 | *ls* | Left side | :const:`ACS_VLINE` |
 +-----------+---------------------+-----------------------+
 | *rs* | Right side | :const:`ACS_VLINE` |
 +-----------+---------------------+-----------------------+
 | *ts* | Top | :const:`ACS_HLINE` |
 +-----------+---------------------+-----------------------+
 | *bs* | Bottom | :const:`ACS_HLINE` |
 +-----------+---------------------+-----------------------+
 | *tl* | Upper-left corner | :const:`ACS_ULCORNER` |
 +-----------+---------------------+-----------------------+
 | *tr* | Upper-right corner | :const:`ACS_URCORNER` |
 +-----------+---------------------+-----------------------+
 | *bl* | Bottom-left corner | :const:`ACS_LLCORNER` |
 +-----------+---------------------+-----------------------+
 | *br* | Bottom-right corner | :const:`ACS_LRCORNER` |
 +-----------+---------------------+-----------------------+

.. method:: window.box([vertch, horch])

 Similar to :meth:`border`, but both *ls* and *rs* are *vertch* and both *ts* and
 *bs* are *horch*. The default corner characters are always used by this function.

.. method:: window.chgat(attr)
 window.chgat(num, attr)
 window.chgat(y, x, attr)
 window.chgat(y, x, num, attr)

 Set the attributes of *num* characters at the current cursor position, or at
 position ``(y, x)`` if supplied. If *num* is not given or is ``-1``,
 the attribute will be set on all the characters to the end of the line. This
 function moves cursor to position ``(y, x)`` if supplied. The changed line
 will be touched using the :meth:`touchline` method so that the contents will
 be redisplayed by the next window refresh.

.. method:: window.clear()

 Like :meth:`erase`, but also cause the whole window to be repainted upon next
 call to :meth:`refresh`.

.. method:: window.clearok(flag)

 If *flag* is ``True``, the next call to :meth:`refresh` will clear the window
 completely.

.. method:: window.clrtobot()

 Erase from cursor to the end of the window: all lines below the cursor are
 deleted, and then the equivalent of :meth:`clrtoeol` is performed.

.. method:: window.clrtoeol()

 Erase from cursor to the end of the line.

.. method:: window.cursyncup()

 Update the current cursor position of all the ancestors of the window to
 reflect the current cursor position of the window.

.. method:: window.delch([y, x])

 Delete any character at ``(y, x)``.

.. method:: window.deleteln()

 Delete the line under the cursor. All following lines are moved up by one line.

.. method:: window.derwin(begin_y, begin_x)
 window.derwin(nlines, ncols, begin_y, begin_x)

 An abbreviation for "derive window", :meth:`derwin` is the same as calling
 :meth:`subwin`, except that *begin_y* and *begin_x* are relative to the origin
 of the window, rather than relative to the entire screen. Return a window
 object for the derived window.

.. method:: window.echochar(ch[, attr])

 Add character *ch* with attribute *attr*, and immediately call :meth:`refresh`
 on the window.

.. method:: window.enclose(y, x)

 Test whether the given pair of screen-relative character-cell coordinates are
 enclosed by the given window, returning ``True`` or ``False``. It is useful for
 determining what subset of the screen windows enclose the location of a mouse
 event.

.. attribute:: window.encoding

 Encoding used to encode method arguments (Unicode strings and characters).
 The encoding attribute is inherited from the parent window when a subwindow
 is created, for example with :meth:`window.subwin`. By default, the locale
 encoding is used (see :func:`locale.getpreferredencoding`).

 .. versionadded:: 3.3

.. method:: window.erase()

 Clear the window.

.. method:: window.getbegyx()

 Return a tuple ``(y, x)`` of co-ordinates of upper-left corner.

.. method:: window.getbkgd()

 Return the given window's current background character/attribute pair.

.. method:: window.getch([y, x])

 Get a character. Note that the integer returned does *not* have to be in ASCII
 range: function keys, keypad keys and so on are represented by numbers higher
 than 255. In no-delay mode, return ``-1`` if there is no input, otherwise
 wait until a key is pressed.

.. method:: window.get_wch([y, x])

 Get a wide character. Return a character for most keys, or an integer for
 function keys, keypad keys, and other special keys.
 In no-delay mode, raise an exception if there is no input.

 .. versionadded:: 3.3

.. method:: window.getkey([y, x])

 Get a character, returning a string instead of an integer, as :meth:`getch`
 does. Function keys, keypad keys and other special keys return a multibyte
 string containing the key name. In no-delay mode, raise an exception if
 there is no input.

.. method:: window.getmaxyx()

 Return a tuple ``(y, x)`` of the height and width of the window.

.. method:: window.getparyx()

 Return the beginning coordinates of this window relative to its parent window
 as a tuple ``(y, x)``. Return ``(-1, -1)`` if this window has no
 parent.

.. method:: window.getstr()
 window.getstr(n)
 window.getstr(y, x)
 window.getstr(y, x, n)

 Read a bytes object from the user, with primitive line editing capacity.

.. method:: window.getyx()

 Return a tuple ``(y, x)`` of current cursor position relative to the window's
 upper-left corner.

.. method:: window.hline(ch, n)
 window.hline(y, x, ch, n)

 Display a horizontal line starting at ``(y, x)`` with length *n* consisting of
 the character *ch*.

.. method:: window.idcok(flag)

 If *flag* is ``False``, curses no longer considers using the hardware insert/delete
 character feature of the terminal; if *flag* is ``True``, use of character insertion
 and deletion is enabled. When curses is first initialized, use of character
 insert/delete is enabled by default.

.. method:: window.idlok(flag)

 If *flag* is ``True``, :mod:`curses` will try and use hardware line
 editing facilities. Otherwise, line insertion/deletion are disabled.

.. method:: window.immedok(flag)

 If *flag* is ``True``, any change in the window image automatically causes the
 window to be refreshed; you no longer have to call :meth:`refresh` yourself.
 However, it may degrade performance considerably, due to repeated calls to
 wrefresh. This option is disabled by default.

.. method:: window.inch([y, x])

 Return the character at the given position in the window. The bottom 8 bits are
 the character proper, and upper bits are the attributes.

.. method:: window.insch(ch[, attr])
 window.insch(y, x, ch[, attr])

 Paint character *ch* at ``(y, x)`` with attributes *attr*, moving the line from
 position *x* right by one character.

.. method:: window.insdelln(nlines)

 Insert *nlines* lines into the specified window above the current line. The
 *nlines* bottom lines are lost. For negative *nlines*, delete *nlines* lines
 starting with the one under the cursor, and move the remaining lines up. The
 bottom *nlines* lines are cleared. The current cursor position remains the
 same.

.. method:: window.insertln()

 Insert a blank line under the cursor. All following lines are moved down by one
 line.

.. method:: window.insnstr(str, n[, attr])
 window.insnstr(y, x, str, n[, attr])

 Insert a character string (as many characters as will fit on the line) before
 the character under the cursor, up to *n* characters. If *n* is zero or
 negative, the entire string is inserted. All characters to the right of the
 cursor are shifted right, with the rightmost characters on the line being lost.
 The cursor position does not change (after moving to *y*, *x*, if specified).

.. method:: window.insstr(str[, attr])
 window.insstr(y, x, str[, attr])

 Insert a character string (as many characters as will fit on the line) before
 the character under the cursor. All characters to the right of the cursor are
 shifted right, with the rightmost characters on the line being lost. The cursor
 position does not change (after moving to *y*, *x*, if specified).

.. method:: window.instr([n])
 window.instr(y, x[, n])

 Return a bytes object of characters, extracted from the window starting at the
 current cursor position, or at *y*, *x* if specified. Attributes are stripped
 from the characters. If *n* is specified, :meth:`instr` returns a string
 at most *n* characters long (exclusive of the trailing NUL).

.. method:: window.is_linetouched(line)

 Return ``True`` if the specified line was modified since the last call to
 :meth:`refresh`; otherwise return ``False``. Raise a :exc:`curses.error`
 exception if *line* is not valid for the given window.

.. method:: window.is_wintouched()

 Return ``True`` if the specified window was modified since the last call to
 :meth:`refresh`; otherwise return ``False``.

.. method:: window.keypad(flag)

 If *flag* is ``True``, escape sequences generated by some keys (keypad, function keys)
 will be interpreted by :mod:`curses`. If *flag* is ``False``, escape sequences will be
 left as is in the input stream.

.. method:: window.leaveok(flag)

 If *flag* is ``True``, cursor is left where it is on update, instead of being at "cursor
 position." This reduces cursor movement where possible. If possible the cursor
 will be made invisible.

 If *flag* is ``False``, cursor will always be at "cursor position" after an update.

.. method:: window.move(new_y, new_x)

 Move cursor to ``(new_y, new_x)``.

.. method:: window.mvderwin(y, x)

 Move the window inside its parent window. The screen-relative parameters of
 the window are not changed. This routine is used to display different parts of
 the parent window at the same physical position on the screen.

.. method:: window.mvwin(new_y, new_x)

 Move the window so its upper-left corner is at ``(new_y, new_x)``.

.. method:: window.nodelay(flag)

 If *flag* is ``True``, :meth:`getch` will be non-blocking.

.. method:: window.notimeout(flag)

 If *flag* is ``True``, escape sequences will not be timed out.

 If *flag* is ``False``, after a few milliseconds, an escape sequence will not be
 interpreted, and will be left in the input stream as is.

.. method:: window.noutrefresh()

 Mark for refresh but wait. This function updates the data structure
 representing the desired state of the window, but does not force an update of
 the physical screen. To accomplish that, call :func:`doupdate`.

.. method:: window.overlay(destwin[, sminrow, smincol, dminrow, dmincol, dmaxrow, dmaxcol])

 Overlay the window on top of *destwin*. The windows need not be the same size,
 only the overlapping region is copied. This copy is non-destructive, which means
 that the current background character does not overwrite the old contents of
 *destwin*.

 To get fine-grained control over the copied region, the second form of
 :meth:`overlay` can be used. *sminrow* and *smincol* are the upper-left
 coordinates of the source window, and the other variables mark a rectangle in
 the destination window.

.. method:: window.overwrite(destwin[, sminrow, smincol, dminrow, dmincol, dmaxrow, dmaxcol])

 Overwrite the window on top of *destwin*. The windows need not be the same size,
 in which case only the overlapping region is copied. This copy is destructive,
 which means that the current background character overwrites the old contents of
 *destwin*.

 To get fine-grained control over the copied region, the second form of
 :meth:`overwrite` can be used. *sminrow* and *smincol* are the upper-left
 coordinates of the source window, the other variables mark a rectangle in the
 destination window.

.. method:: window.putwin(file)

 Write all data associated with the window into the provided file object. This
 information can be later retrieved using the :func:`getwin` function.

.. method:: window.redrawln(beg, num)

 Indicate that the *num* screen lines, starting at line *beg*, are corrupted and
 should be completely redrawn on the next :meth:`refresh` call.

.. method:: window.redrawwin()

 Touch the entire window, causing it to be completely redrawn on the next
 :meth:`refresh` call.

.. method:: window.refresh([pminrow, pmincol, sminrow, smincol, smaxrow, smaxcol])

 Update the display immediately (sync actual screen with previous
 drawing/deleting methods).

 The 6 optional arguments can only be specified when the window is a pad created
 with :func:`newpad`. The additional parameters are needed to indicate what part
 of the pad and screen are involved. *pminrow* and *pmincol* specify the upper
 left-hand corner of the rectangle to be displayed in the pad. *sminrow*,
 *smincol*, *smaxrow*, and *smaxcol* specify the edges of the rectangle to be
 displayed on the screen. The lower right-hand corner of the rectangle to be
 displayed in the pad is calculated from the screen coordinates, since the
 rectangles must be the same size. Both rectangles must be entirely contained
 within their respective structures. Negative values of *pminrow*, *pmincol*,
 *sminrow*, or *smincol* are treated as if they were zero.

.. method:: window.resize(nlines, ncols)

 Reallocate storage for a curses window to adjust its dimensions to the
 specified values. If either dimension is larger than the current values, the
 window's data is filled with blanks that have the current background
 rendition (as set by :meth:`bkgdset`) merged into them.

.. method:: window.scroll([lines=1])

 Scroll the screen or scrolling region upward by *lines* lines.

.. method:: window.scrollok(flag)

 Control what happens when the cursor of a window is moved off the edge of the
 window or scrolling region, either as a result of a newline action on the bottom
 line, or typing the last character of the last line. If *flag* is ``False``, the
 cursor is left on the bottom line. If *flag* is ``True``, the window is scrolled up
 one line. Note that in order to get the physical scrolling effect on the
 terminal, it is also necessary to call :meth:`idlok`.

.. method:: window.setscrreg(top, bottom)

 Set the scrolling region from line *top* to line *bottom*. All scrolling actions
 will take place in this region.

.. method:: window.standend()

 Turn off the standout attribute. On some terminals this has the side effect of
 turning off all attributes.

.. method:: window.standout()

 Turn on attribute *A_STANDOUT*.

.. method:: window.subpad(begin_y, begin_x)
 window.subpad(nlines, ncols, begin_y, begin_x)

 Return a sub-window, whose upper-left corner is at ``(begin_y, begin_x)``, and
 whose width/height is *ncols*/*nlines*.

.. method:: window.subwin(begin_y, begin_x)
 window.subwin(nlines, ncols, begin_y, begin_x)

 Return a sub-window, whose upper-left corner is at ``(begin_y, begin_x)``, and
 whose width/height is *ncols*/*nlines*.

 By default, the sub-window will extend from the specified position to the lower
 right corner of the window.

.. method:: window.syncdown()

 Touch each location in the window that has been touched in any of its ancestor
 windows. This routine is called by :meth:`refresh`, so it should almost never
 be necessary to call it manually.

.. method:: window.syncok(flag)

 If *flag* is ``True``, then :meth:`syncup` is called automatically
 whenever there is a change in the window.

.. method:: window.syncup()

 Touch all locations in ancestors of the window that have been changed in the
 window.

.. method:: window.timeout(delay)

 Set blocking or non-blocking read behavior for the window. If *delay* is
 negative, blocking read is used (which will wait indefinitely for input). If
 *delay* is zero, then non-blocking read is used, and :meth:`getch` will
 return ``-1`` if no input is waiting. If *delay* is positive, then
 :meth:`getch` will block for *delay* milliseconds, and return ``-1`` if there is
 still no input at the end of that time.

.. method:: window.touchline(start, count[, changed])

 Pretend *count* lines have been changed, starting with line *start*. If
 *changed* is supplied, it specifies whether the affected lines are marked as
 having been changed (*changed*\ ``=True``) or unchanged (*changed*\ ``=False``).

.. method:: window.touchwin()

 Pretend the whole window has been changed, for purposes of drawing
 optimizations.

.. method:: window.untouchwin()

 Mark all lines in the window as unchanged since the last call to
 :meth:`refresh`.

.. method:: window.vline(ch, n)
 window.vline(y, x, ch, n)

 Display a vertical line starting at ``(y, x)`` with length *n* consisting of the
 character *ch*.

Constants

The :mod:`curses` module defines the following data members:

.. data:: ERR

 Some curses routines that return an integer, such as :meth:`~window.getch`, return
 :const:`ERR` upon failure.

.. data:: OK

 Some curses routines that return an integer, such as :func:`napms`, return
 :const:`OK` upon success.

.. data:: version

 A bytes object representing the current version of the module. Also available as
 :const:`__version__`.

.. data:: ncurses_version

 A named tuple containing the three components of the ncurses library
 version: *major*, *minor*, and *patch*. All values are integers. The
 components can also be accessed by name, so ``curses.ncurses_version[0]``
 is equivalent to ``curses.ncurses_version.major`` and so on.

 Availability: if the ncurses library is used.

 .. versionadded:: 3.8

Some constants are available to specify character cell attributes. The exact constants available are system dependent.

.. versionadded:: 3.7
 ``A_ITALIC`` was added.

Several constants are available to extract corresponding attributes returned by some methods.

Keys are referred to by integer constants with names starting with KEY_. The exact keycaps available are system dependent.

On VT100s and their software emulations, such as X terminal emulators, there are normally at least four function keys (:const:`KEY_F1`, :const:`KEY_F2`, :const:`KEY_F3`, :const:`KEY_F4`) available, and the arrow keys mapped to :const:`KEY_UP`, :const:`KEY_DOWN`, :const:`KEY_LEFT` and :const:`KEY_RIGHT` in the obvious way. If your machine has a PC keyboard, it is safe to expect arrow keys and twelve function keys (older PC keyboards may have only ten function keys); also, the following keypad mappings are standard:

The following table lists characters from the alternate character set. These are inherited from the VT100 terminal, and will generally be available on software emulations such as X terminals. When there is no graphic available, curses falls back on a crude printable ASCII approximation.

The following table lists the predefined colors:

:mod:`curses.textpad` --- Text input widget for curses programs

.. module:: curses.textpad
 :synopsis: Emacs-like input editing in a curses window.

.. moduleauthor:: Eric Raymond <esr@thyrsus.com>

.. sectionauthor:: Eric Raymond <esr@thyrsus.com>

The :mod:`curses.textpad` module provides a :class:`Textbox` class that handles elementary text editing in a curses window, supporting a set of keybindings resembling those of Emacs (thus, also of Netscape Navigator, BBedit 6.x, FrameMaker, and many other programs). The module also provides a rectangle-drawing function useful for framing text boxes or for other purposes.

The module :mod:`curses.textpad` defines the following function:

.. function:: rectangle(win, uly, ulx, lry, lrx)

 Draw a rectangle. The first argument must be a window object; the remaining
 arguments are coordinates relative to that window. The second and third
 arguments are the y and x coordinates of the upper left hand corner of the
 rectangle to be drawn; the fourth and fifth arguments are the y and x
 coordinates of the lower right hand corner. The rectangle will be drawn using
 VT100/IBM PC forms characters on terminals that make this possible (including
 xterm and most other software terminal emulators). Otherwise it will be drawn
 with ASCII dashes, vertical bars, and plus signs.

Textbox objects

You can instantiate a :class:`Textbox` object as follows:

Return a textbox widget object. The win argument should be a curses :ref:`window <curses-window-objects>` object in which the textbox is to be contained. The edit cursor of the textbox is initially located at the upper left hand corner of the containing window, with coordinates (0, 0). The instance's :attr:`stripspaces` flag is initially on.

:class:`Textbox` objects have the following methods:

.. method:: edit([validator])

 This is the entry point you will normally use. It accepts editing
 keystrokes until one of the termination keystrokes is entered. If
 *validator* is supplied, it must be a function. It will be called for
 each keystroke entered with the keystroke as a parameter; command dispatch
 is done on the result. This method returns the window contents as a
 string; whether blanks in the window are included is affected by the
 :attr:`stripspaces` attribute.

.. method:: do_command(ch)

 Process a single command keystroke. Here are the supported special
 keystrokes:

 +------------------+-------------------------------------------+
 | Keystroke | Action |
 +==================+===========================================+
 | :kbd:`Control-A` | Go to left edge of window. |
 +------------------+-------------------------------------------+
 | :kbd:`Control-B` | Cursor left, wrapping to previous line if |
 | | appropriate. |
 +------------------+-------------------------------------------+
 | :kbd:`Control-D` | Delete character under cursor. |
 +------------------+-------------------------------------------+
 | :kbd:`Control-E` | Go to right edge (stripspaces off) or end |
 | | of line (stripspaces on). |
 +------------------+-------------------------------------------+
 | :kbd:`Control-F` | Cursor right, wrapping to next line when |
 | | appropriate. |
 +------------------+-------------------------------------------+
 | :kbd:`Control-G` | Terminate, returning the window contents. |
 +------------------+-------------------------------------------+
 | :kbd:`Control-H` | Delete character backward. |
 +------------------+-------------------------------------------+
 | :kbd:`Control-J` | Terminate if the window is 1 line, |
 | | otherwise insert newline. |
 +------------------+-------------------------------------------+
 | :kbd:`Control-K` | If line is blank, delete it, otherwise |
 | | clear to end of line. |
 +------------------+-------------------------------------------+
 | :kbd:`Control-L` | Refresh screen. |
 +------------------+-------------------------------------------+
 | :kbd:`Control-N` | Cursor down; move down one line. |
 +------------------+-------------------------------------------+
 | :kbd:`Control-O` | Insert a blank line at cursor location. |
 +------------------+-------------------------------------------+
 | :kbd:`Control-P` | Cursor up; move up one line. |
 +------------------+-------------------------------------------+

 Move operations do nothing if the cursor is at an edge where the movement
 is not possible. The following synonyms are supported where possible:

 +------------------------+------------------+
 | Constant | Keystroke |
 +========================+==================+
 | :const:`KEY_LEFT` | :kbd:`Control-B` |
 +------------------------+------------------+
 | :const:`KEY_RIGHT` | :kbd:`Control-F` |
 +------------------------+------------------+
 | :const:`KEY_UP` | :kbd:`Control-P` |
 +------------------------+------------------+
 | :const:`KEY_DOWN` | :kbd:`Control-N` |
 +------------------------+------------------+
 | :const:`KEY_BACKSPACE` | :kbd:`Control-h` |
 +------------------------+------------------+

 All other keystrokes are treated as a command to insert the given
 character and move right (with line wrapping).

.. method:: gather()

 Return the window contents as a string; whether blanks in the
 window are included is affected by the :attr:`stripspaces` member.

.. attribute:: stripspaces

 This attribute is a flag which controls the interpretation of blanks in
 the window. When it is on, trailing blanks on each line are ignored; any
 cursor motion that would land the cursor on a trailing blank goes to the
 end of that line instead, and trailing blanks are stripped when the window
 contents are gathered.

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