#17700: update the curses HOWTO for 3.x

Doc/howto/curses.rst

@@ -5,39 +5,43 @@
 **********************************
 
 :Author: A.M. Kuchling, Eric S. Raymond
-:Release: 2.03
+:Release: 2.04
 
 
 .. topic:: Abstract
 
-   This document describes how to write text-mode programs with Python 2.x, using
-   the :mod:`curses` extension module to control the display.
+   This document describes how to use the :mod:`curses` extension
+   module to control text-mode displays.
 
 
 What is curses?
 ===============
 
 The curses library supplies a terminal-independent screen-painting and
-keyboard-handling facility for text-based terminals; such terminals include
-VT100s, the Linux console, and the simulated terminal provided by X11 programs
-such as xterm and rxvt.  Display terminals support various control codes to
-perform common operations such as moving the cursor, scrolling the screen, and
-erasing areas.  Different terminals use widely differing codes, and often have
-their own minor quirks.
-
-In a world of X displays, one might ask "why bother"?  It's true that
-character-cell display terminals are an obsolete technology, but there are
-niches in which being able to do fancy things with them are still valuable.  One
-is on small-footprint or embedded Unixes that don't carry an X server.  Another
-is for tools like OS installers and kernel configurators that may have to run
-before X is available.
-
-The curses library hides all the details of different terminals, and provides
-the programmer with an abstraction of a display, containing multiple
-non-overlapping windows.  The contents of a window can be changed in various
-ways-- adding text, erasing it, changing its appearance--and the curses library
-will automagically figure out what control codes need to be sent to the terminal
-to produce the right output.
+keyboard-handling facility for text-based terminals; such terminals
+include VT100s, the Linux console, and the simulated terminal provided
+by various programs.  Display terminals support various control codes
+to perform common operations such as moving the cursor, scrolling the
+screen, and erasing areas.  Different terminals use widely differing
+codes, and often have their own minor quirks.
+
+In a world of graphical displays, one might ask "why bother"?  It's
+true that character-cell display terminals are an obsolete technology,
+but there are niches in which being able to do fancy things with them
+are still valuable.  One niche is on small-footprint or embedded
+Unixes that don't run an X server.  Another is tools such as OS
+installers and kernel configurators that may have to run before any
+graphical support is available.
+
+The curses library provides fairly basic functionality, providing the
+programmer with an abstraction of a display containing multiple
+non-overlapping windows of text.  The contents of a window can be
+changed in various ways---adding text, erasing it, changing its
+appearance---and the curses library will figure out what control codes
+need to be sent to the terminal to produce the right output.  curses
+doesn't provide many user-interface concepts such as buttons, checkboxes,
+or dialogs; if you need such features, consider a user interface library such as
+`Urwid <https://pypi.python.org/pypi/urwid/>`_.
 
 The curses library was originally written for BSD Unix; the later System V
 versions of Unix from AT&T added many enhancements and new functions. BSD curses
@@ -49,10 +53,13 @@ code, all the functions described here will probably be available.  The older
 versions of curses carried by some proprietary Unixes may not support
 everything, though.
 
-No one has made a Windows port of the curses module.  On a Windows platform, try
-the Console module written by Fredrik Lundh.  The Console module provides
-cursor-addressable text output, plus full support for mouse and keyboard input,
-and is available from http://effbot.org/zone/console-index.htm.
+The Windows version of Python doesn't include the :mod:`curses`
+module.  A ported version called `UniCurses
+<https://pypi.python.org/pypi/UniCurses>`_ is available.  You could
+also try `the Console module <http://effbot.org/zone/console-index.htm>`_
+written by Fredrik Lundh, which doesn't
+use the same API as curses but provides cursor-addressable text output
+and full support for mouse and keyboard input.
 
 
 The Python curses module
@@ -61,11 +68,12 @@ The Python curses module
 Thy Python module is a fairly simple wrapper over the C functions provided by
 curses; if you're already familiar with curses programming in C, it's really
 easy to transfer that knowledge to Python.  The biggest difference is that the
-Python interface makes things simpler, by merging different C functions such as
-:func:`addstr`, :func:`mvaddstr`, :func:`mvwaddstr`, into a single
-:meth:`addstr` method.  You'll see this covered in more detail later.
+Python interface makes things simpler by merging different C functions such as
+:c:func:`addstr`, :c:func:`mvaddstr`, and :c:func:`mvwaddstr` into a single
+:meth:`~curses.window.addstr` method.  You'll see this covered in more
+detail later.
 
-This HOWTO is simply an introduction to writing text-mode programs with curses
+This HOWTO is an introduction to writing text-mode programs with curses
 and Python. It doesn't attempt to be a complete guide to the curses API; for
 that, see the Python library guide's section on ncurses, and the C manual pages
 for ncurses.  It will, however, give you the basic ideas.
@@ -74,25 +82,27 @@ for ncurses.  It will, however, give you the basic ideas.
 Starting and ending a curses application
 ========================================
 
-Before doing anything, curses must be initialized.  This is done by calling the
-:func:`initscr` function, which will determine the terminal type, send any
-required setup codes to the terminal, and create various internal data
-structures.  If successful, :func:`initscr` returns a window object representing
-the entire screen; this is usually called ``stdscr``, after the name of the
+Before doing anything, curses must be initialized.  This is done by
+calling the :func:`~curses.initscr` function, which will determine the
+terminal type, send any required setup codes to the terminal, and
+create various internal data structures.  If successful,
+:func:`initscr` returns a window object representing the entire
+screen; this is usually called ``stdscr`` after the name of the
 corresponding C variable. ::
 
    import curses
    stdscr = curses.initscr()
 
-Usually curses applications turn off automatic echoing of keys to the screen, in
-order to be able to read keys and only display them under certain circumstances.
-This requires calling the :func:`noecho` function. ::
+Usually curses applications turn off automatic echoing of keys to the
+screen, in order to be able to read keys and only display them under
+certain circumstances.  This requires calling the
+:func:`~curses.noecho` function. ::
 
    curses.noecho()
 
-Applications will also commonly need to react to keys instantly, without
-requiring the Enter key to be pressed; this is called cbreak mode, as opposed to
-the usual buffered input mode. ::
+Applications will also commonly need to react to keys instantly,
+without requiring the Enter key to be pressed; this is called cbreak
+mode, as opposed to the usual buffered input mode. ::
 
    curses.cbreak()
 
@@ -103,12 +113,14 @@ curses can do it for you, returning a special value such as
 :const:`curses.KEY_LEFT`.  To get curses to do the job, you'll have to enable
 keypad mode. ::
 
-   stdscr.keypad(1)
+   stdscr.keypad(True)
 
 Terminating a curses application is much easier than starting one. You'll need
-to call  ::
+to call::
 
-   curses.nocbreak(); stdscr.keypad(0); curses.echo()
+   curses.nocbreak()
+   stdscr.keypad(False)
+   curses.echo()
 
 to reverse the curses-friendly terminal settings. Then call the :func:`endwin`
 function to restore the terminal to its original operating mode. ::
@@ -122,102 +134,147 @@ raises an uncaught exception.  Keys are no longer echoed to the screen when
 you type them, for example, which makes using the shell difficult.
 
 In Python you can avoid these complications and make debugging much easier by
-importing the module :mod:`curses.wrapper`.  It supplies a :func:`wrapper`
-function that takes a callable.  It does the initializations described above,
-and also initializes colors if color support is present.  It then runs your
-provided callable and finally deinitializes appropriately.  The callable is
-called inside a try-catch clause which catches exceptions, performs curses
-deinitialization, and then passes the exception upwards.  Thus, your terminal
-won't be left in a funny state on exception.
+importing the :func:`curses.wrapper` function and using it like this::
+
+   from curses import wrapper
+
+   def main(stdscr):
+       # Clear screen
+       stdscr.clear()
+
+       # This raises ZeroDivisionError when i == 10.
+       for i in range(0, 10):
+           v = i-10
+           stdscr.addstr(i, 0, '10 divided by {} is {}'.format(v, 10/v))
+
+       stdscr.refresh()
+       stdscr.getkey()
+
+   wrapper(main)
+
+The :func:`wrapper` function takes a callable object and does the
+initializations described above, also initializing colors if color
+support is present.  :func:`wrapper` then runs your provided callable.
+Once the callable returns, :func:`wrapper` will restore the original
+state of the terminal.  The callable is called inside a
+:keyword:`try`...\ :keyword:`except` that catches exceptions, restores
+the state of the terminal, and then re-raises the exception.  Therefore
+your terminal won't be left in a funny state on exception and you'll be
+able to read the exception's message and traceback.
 
 
 Windows and Pads
 ================
 
 Windows are the basic abstraction in curses.  A window object represents a
-rectangular area of the screen, and supports various methods to display text,
+rectangular area of the screen, and supports methods to display text,
 erase it, allow the user to input strings, and so forth.
 
-The ``stdscr`` object returned by the :func:`initscr` function is a window
-object that covers the entire screen.  Many programs may need only this single
-window, but you might wish to divide the screen into smaller windows, in order
-to redraw or clear them separately. The :func:`newwin` function creates a new
-window of a given size, returning the new window object. ::
+The ``stdscr`` object returned by the :func:`initscr` function is a
+window object that covers the entire screen.  Many programs may need
+only this single window, but you might wish to divide the screen into
+smaller windows, in order to redraw or clear them separately. The
+:func:`~curses.newwin` function creates a new window of a given size,
+returning the new window object. ::
 
    begin_x = 20 ; begin_y = 7
    height = 5 ; width = 40
    win = curses.newwin(height, width, begin_y, begin_x)
 
-A word about the coordinate system used in curses: coordinates are always passed
-in the order *y,x*, and the top-left corner of a window is coordinate (0,0).
-This breaks a common convention for handling coordinates, where the *x*
-coordinate usually comes first.  This is an unfortunate difference from most
-other computer applications, but it's been part of curses since it was first
-written, and it's too late to change things now.
-
-When you call a method to display or erase text, the effect doesn't immediately
-show up on the display.  This is because curses was originally written with slow
-300-baud terminal connections in mind; with these terminals, minimizing the time
-required to redraw the screen is very important.  This lets curses accumulate
-changes to the screen, and display them in the most efficient manner.  For
-example, if your program displays some characters in a window, and then clears
-the window, there's no need to send the original characters because they'd never
-be visible.
-
-Accordingly, curses requires that you explicitly tell it to redraw windows,
-using the :func:`refresh` method of window objects.  In practice, this doesn't
+Note that the coordinate system used in curses is unusual.
+Coordinates are always passed in the order *y,x*, and the top-left
+corner of a window is coordinate (0,0).  This breaks the normal
+convention for handling coordinates where the *x* coordinate comes
+first.  This is an unfortunate difference from most other computer
+applications, but it's been part of curses since it was first written,
+and it's too late to change things now.
+
+Your application can determine the size of the screen by using the
+:data:`curses.LINES` and :data:`curses.COLS` variables to obtain the *y* and
+*x* sizes.  Legal coordinates will then extend from ``(0,0)`` to
+``(curses.LINES - 1, curses.COLS - 1)``.
+
+When you call a method to display or erase text, the effect doesn't
+immediately show up on the display.  Instead you must call the
+:meth:`~curses.window.refresh` method of window objects to update the
+screen.
+
+This is because curses was originally written with slow 300-baud
+terminal connections in mind; with these terminals, minimizing the
+time required to redraw the screen was very important.  Instead curses
+accumulates changes to the screen and displays them in the most
+efficient manner when you call :meth:`refresh`.  For example, if your
+program displays some text in a window and then clears the window,
+there's no need to send the original text because they're never
+visible.
+
+In practice, explicitly telling curses to redraw a window doesn't
 really complicate programming with curses much. Most programs go into a flurry
 of activity, and then pause waiting for a keypress or some other action on the
 part of the user.  All you have to do is to be sure that the screen has been
-redrawn before pausing to wait for user input, by simply calling
-``stdscr.refresh()`` or the :func:`refresh` method of some other relevant
+redrawn before pausing to wait for user input, by first calling
+``stdscr.refresh()`` or the :meth:`refresh` method of some other relevant
 window.
 
 A pad is a special case of a window; it can be larger than the actual display
-screen, and only a portion of it displayed at a time. Creating a pad simply
+screen, and only a portion of the pad displayed at a time. Creating a pad
 requires the pad's height and width, while refreshing a pad requires giving the
 coordinates of the on-screen area where a subsection of the pad will be
-displayed.   ::
+displayed.  ::
 
    pad = curses.newpad(100, 100)
-   #  These loops fill the pad with letters; this is
+   # These loops fill the pad with letters; addch() is
    # explained in the next section
-   for y in range(0, 100):
-       for x in range(0, 100):
-           try: pad.addch(y,x, ord('a') + (x*x+y*y) % 26 )
-           except curses.error: pass
-
-   #  Displays a section of the pad in the middle of the screen
+   for y in range(0, 99):
+       for x in range(0, 99):
+           pad.addch(y,x, ord('a') + (x*x+y*y) % 26 )
+
+   # Displays a section of the pad in the middle of the screen.
+   # (0,0) : coordinate of upper-left corner of pad area to display.
+   # (5,5) : coordinate of upper-left corner of window area to be filled
+   #         with pad content.
+   # (20, 75) : coordinate of lower-right corner of window area to be
+   #          : filled with pad content.
    pad.refresh( 0,0, 5,5, 20,75)
 
-The :func:`refresh` call displays a section of the pad in the rectangle
+The :meth:`refresh` call displays a section of the pad in the rectangle
 extending from coordinate (5,5) to coordinate (20,75) on the screen; the upper
 left corner of the displayed section is coordinate (0,0) on the pad.  Beyond
 that difference, pads are exactly like ordinary windows and support the same
 methods.
 
-If you have multiple windows and pads on screen there is a more efficient way to
-go, which will prevent annoying screen flicker at refresh time.  Use the
-:meth:`noutrefresh` method of each window to update the data structure
-representing the desired state of the screen; then change the physical screen to
-match the desired state in one go with the function :func:`doupdate`.  The
-normal :meth:`refresh` method calls :func:`doupdate` as its last act.
+If you have multiple windows and pads on screen there is a more
+efficient way to update the screen and prevent annoying screen flicker
+as each part of the screen gets updated.  :meth:`refresh` actually
+does two things:
+
+1) Calls the :meth:`~curses.window.noutrefresh` method of each window
+   to update an underlying data structure representing the desired
+   state of the screen.
+2) Calls the function :func:`~curses.doupdate` function to change the
+   physical screen to match the desired state recorded in the data structure.
+
+Instead you can call :meth:`noutrefresh` on a number of windows to
+update the data structure, and then call :func:`doupdate` to update
+the screen.
 
 
 Displaying Text
 ===============
 
-From a C programmer's point of view, curses may sometimes look like a twisty
-maze of functions, all subtly different.  For example, :func:`addstr` displays a
-string at the current cursor location in the ``stdscr`` window, while
-:func:`mvaddstr` moves to a given y,x coordinate first before displaying the
-string. :func:`waddstr` is just like :func:`addstr`, but allows specifying a
-window to use, instead of using ``stdscr`` by default. :func:`mvwaddstr` follows
-similarly.
+From a C programmer's point of view, curses may sometimes look like a
+twisty maze of functions, all subtly different.  For example,
+:c:func:`addstr` displays a string at the current cursor location in
+the ``stdscr`` window, while :c:func:`mvaddstr` moves to a given y,x
+coordinate first before displaying the string. :c:func:`waddstr` is just
+like :func:`addstr`, but allows specifying a window to use instead of
+using ``stdscr`` by default. :c:func:`mvwaddstr` allows specifying both
+a window and a coordinate.
 
-Fortunately the Python interface hides all these details; ``stdscr`` is a window
-object like any other, and methods like :func:`addstr` accept multiple argument
-forms.  Usually there are four different forms.
+Fortunately the Python interface hides all these details.  ``stdscr``
+is a window object like any other, and methods such as :meth:`addstr`
+accept multiple argument forms.  Usually there are four different
+forms.
 
 +---------------------------------+-----------------------------------------------+
 | Form                            | Description                                   |
@@ -236,17 +293,26 @@ forms.  Usually there are four different forms.
 |                                 | display *str* or *ch*, using attribute *attr* |
 +---------------------------------+-----------------------------------------------+
 
-Attributes allow displaying text in highlighted forms, such as in boldface,
+Attributes allow displaying text in highlighted forms such as boldface,
 underline, reverse code, or in color.  They'll be explained in more detail in
 the next subsection.
 
-The :func:`addstr` function takes a Python string as the value to be displayed,
-while the :func:`addch` functions take a character, which can be either a Python
-string of length 1 or an integer.  If it's a string, you're limited to
-displaying characters between 0 and 255.  SVr4 curses provides constants for
-extension characters; these constants are integers greater than 255.  For
-example, :const:`ACS_PLMINUS` is a +/- symbol, and :const:`ACS_ULCORNER` is the
-upper left corner of a box (handy for drawing borders).
+
+The :meth:`~curses.window.addstr` method takes a Python string or
+bytestring as the value to be displayed.  The contents of bytestrings
+are sent to the terminal as-is.  Strings are encoded to bytes using
+the value of the window's :attr:`encoding` attribute; this defaults to
+the default system encoding as returned by
+:func:`locale.getpreferredencoding`.
+
+The :meth:`~curses.window.addch` methods take a character, which can be
+either a string of length 1, a bytestring of length 1, or an integer.
+
+Constants are provided for extension characters; these constants are
+integers greater than 255.  For example, :const:`ACS_PLMINUS` is a +/-
+symbol, and :const:`ACS_ULCORNER` is the upper left corner of a box
+(handy for drawing borders).  You can also use the appropriate Unicode
+character.
 
 Windows remember where the cursor was left after the last operation, so if you
 leave out the *y,x* coordinates, the string or character will be displayed
@@ -256,10 +322,11 @@ you may want to ensure that the cursor is positioned in some location where it
 won't be distracting; it can be confusing to have the cursor blinking at some
 apparently random location.
 
-If your application doesn't need a blinking cursor at all, you can call
-``curs_set(0)`` to make it invisible.  Equivalently, and for compatibility with
-older curses versions, there's a ``leaveok(bool)`` function.  When *bool* is
-true, the curses library will attempt to suppress the flashing cursor, and you
+If your application doesn't need a blinking cursor at all, you can
+call ``curs_set(False)`` to make it invisible.  For compatibility
+with older curses versions, there's a ``leaveok(bool)`` function
+that's a synonym for :func:`curs_set`.  When *bool* is true, the
+curses library will attempt to suppress the flashing cursor, and you
 won't need to worry about leaving it in odd locations.
 
 
@@ -267,15 +334,16 @@ Attributes and Color
 --------------------
 
 Characters can be displayed in different ways.  Status lines in a text-based
-application are commonly shown in reverse video; a text viewer may need to
+application are commonly shown in reverse video, or a text viewer may need to
 highlight certain words.  curses supports this by allowing you to specify an
 attribute for each cell on the screen.
 
-An attribute is an integer, each bit representing a different attribute.  You can
-try to display text with multiple attribute bits set, but curses doesn't
-guarantee that all the possible combinations are available, or that they're all
-visually distinct.  That depends on the ability of the terminal being used, so
-it's safest to stick to the most commonly available attributes, listed here.
+An attribute is an integer, each bit representing a different
+attribute.  You can try to display text with multiple attribute bits
+set, but curses doesn't guarantee that all the possible combinations
+are available, or that they're all visually distinct.  That depends on
+the ability of the terminal being used, so it's safest to stick to the
+most commonly available attributes, listed here.
 
 +----------------------+--------------------------------------+
 | Attribute            | Description                          |
@@ -306,7 +374,7 @@ xterms.
 
 To use color, you must call the :func:`start_color` function soon after calling
 :func:`initscr`, to initialize the default color set (the
-:func:`curses.wrapper.wrapper` function does this automatically).  Once that's
+:func:`curses.wrapper` function does this automatically).  Once that's
 done, the :func:`has_colors` function returns TRUE if the terminal in use can
 actually display color.  (Note: curses uses the American spelling 'color',
 instead of the Canadian/British spelling 'colour'.  If you're used to the
@@ -325,15 +393,16 @@ An example, which displays a line of text using color pair 1::
    stdscr.refresh()
 
 As I said before, a color pair consists of a foreground and background color.
-:func:`start_color` initializes 8 basic colors when it activates color mode.
-They are: 0:black, 1:red, 2:green, 3:yellow, 4:blue, 5:magenta, 6:cyan, and
-7:white.  The curses module defines named constants for each of these colors:
-:const:`curses.COLOR_BLACK`, :const:`curses.COLOR_RED`, and so forth.
-
 The ``init_pair(n, f, b)`` function changes the definition of color pair *n*, to
 foreground color f and background color b.  Color pair 0 is hard-wired to white
 on black, and cannot be changed.
 
+Colors are numbered, and :func:`start_color` initializes 8 basic
+colors when it activates color mode.  They are: 0:black, 1:red,
+2:green, 3:yellow, 4:blue, 5:magenta, 6:cyan, and 7:white.  The :mod:`curses`
+module defines named constants for each of these colors:
+:const:`curses.COLOR_BLACK`, :const:`curses.COLOR_RED`, and so forth.
+
 Let's put all this together. To change color 1 to red text on a white
 background, you would call::
 
@@ -350,87 +419,130 @@ RGB value.  This lets you change color 1, which is usually red, to purple or
 blue or any other color you like.  Unfortunately, the Linux console doesn't
 support this, so I'm unable to try it out, and can't provide any examples.  You
 can check if your terminal can do this by calling :func:`can_change_color`,
-which returns TRUE if the capability is there.  If you're lucky enough to have
+which returns True if the capability is there.  If you're lucky enough to have
 such a talented terminal, consult your system's man pages for more information.
 
 
 User Input
 ==========
 
-The curses library itself offers only very simple input mechanisms. Python's
-support adds a text-input widget that makes up some of the lack.
-
-The most common way to get input to a window is to use its :meth:`getch` method.
-:meth:`getch` pauses and waits for the user to hit a key, displaying it if
-:func:`echo` has been called earlier.  You can optionally specify a coordinate
-to which the cursor should be moved before pausing.
-
-It's possible to change this behavior with the method :meth:`nodelay`. After
-``nodelay(1)``, :meth:`getch` for the window becomes non-blocking and returns
-``curses.ERR`` (a value of -1) when no input is ready.  There's also a
-:func:`halfdelay` function, which can be used to (in effect) set a timer on each
-:meth:`getch`; if no input becomes available within a specified
-delay (measured in tenths of a second), curses raises an exception.
+The C curses library offers only very simple input mechanisms. Python's
+:mod:`curses` module adds a basic text-input widget.  (Other libraries
+such as `Urwid <https://pypi.python.org/pypi/urwid/>`_ have more extensive
+collections of widgets.)
+
+There are two methods for getting input from a window:
+
+* :meth:`~curses.window.getch` refreshes the screen and then waits for
+  the user to hit a key, displaying the key if :func:`echo` has been
+  called earlier.  You can optionally specify a coordinate to which
+  the cursor should be moved before pausing.
+
+* :meth:`~curses.window.getkey` does the same thing but converts the
+  integer to a string.  Individual characters are returned as
+  1-character strings, and special keys such as function keys return
+  longer strings containing a key name such as ``KEY_UP`` or ``^G``.
+
+It's possible to not wait for the user using the
+:meth:`~curses.window.nodelay` window method. After ``nodelay(True)``,
+:meth:`getch` and :meth:`getkey` for the window become
+non-blocking. To signal that no input is ready, :meth:`getch` returns
+``curses.ERR`` (a value of -1) and :meth:`getkey` raises an exception.
+There's also a :func:`~curses.halfdelay` function, which can be used to (in
+effect) set a timer on each :meth:`getch`; if no input becomes
+available within a specified delay (measured in tenths of a second),
+curses raises an exception.
 
 The :meth:`getch` method returns an integer; if it's between 0 and 255, it
 represents the ASCII code of the key pressed.  Values greater than 255 are
 special keys such as Page Up, Home, or the cursor keys. You can compare the
 value returned to constants such as :const:`curses.KEY_PPAGE`,
-:const:`curses.KEY_HOME`, or :const:`curses.KEY_LEFT`.  Usually the main loop of
-your program will look something like this::
+:const:`curses.KEY_HOME`, or :const:`curses.KEY_LEFT`.  The main loop of
+your program may look something like this::
 
    while True:
        c = stdscr.getch()
-       if c == ord('p'): PrintDocument()
-       elif c == ord('q'): break  # Exit the while()
-       elif c == curses.KEY_HOME: x = y = 0
+       if c == ord('p'):
+           PrintDocument()
+       elif c == ord('q'):
+           break  # Exit the while loop
+       elif c == curses.KEY_HOME:
+           x = y = 0
 
 The :mod:`curses.ascii` module supplies ASCII class membership functions that
-take either integer or 1-character-string arguments; these may be useful in
-writing more readable tests for your command interpreters.  It also supplies
+take either integer or 1-character string arguments; these may be useful in
+writing more readable tests for such loops.  It also supplies
 conversion functions  that take either integer or 1-character-string arguments
 and return the same type.  For example, :func:`curses.ascii.ctrl` returns the
 control character corresponding to its argument.
 
-There's also a method to retrieve an entire string, :const:`getstr()`.  It isn't
-used very often, because its functionality is quite limited; the only editing
-keys available are the backspace key and the Enter key, which terminates the
-string.  It can optionally be limited to a fixed number of characters. ::
+There's also a method to retrieve an entire string,
+:meth:`~curses.window.getstr`.  It isn't used very often, because its
+functionality is quite limited; the only editing keys available are
+the backspace key and the Enter key, which terminates the string.  It
+can optionally be limited to a fixed number of characters. ::
 
    curses.echo()            # Enable echoing of characters
 
    # Get a 15-character string, with the cursor on the top line
    s = stdscr.getstr(0,0, 15)
 
-The Python :mod:`curses.textpad` module supplies something better. With it, you
-can turn a window into a text box that supports an Emacs-like set of
-keybindings.  Various methods of :class:`Textbox` class support editing with
-input validation and gathering the edit results either with or without trailing
-spaces.   See the library documentation on :mod:`curses.textpad` for the
-details.
+The :mod:`curses.textpad` module supplies a text box that supports an
+Emacs-like set of keybindings.  Various methods of the
+:class:`~curses.textpad.Textbox` class support editing with input
+validation and gathering the edit results either with or without
+trailing spaces.  Here's an example::
+
+   import curses
+   from curses.textpad import Textbox, rectangle
 
+   def main(stdscr):
+       stdscr.addstr(0, 0, "Enter IM message: (hit Ctrl-G to send)")
 
-For More Information
-====================
+       editwin = curses.newwin(5,30, 2,1)
+       rectangle(stdscr, 1,0, 1+5+1, 1+30+1)
+       stdscr.refresh()
 
-This HOWTO didn't cover some advanced topics, such as screen-scraping or
-capturing mouse events from an xterm instance.  But the Python library page for
-the curses modules is now pretty complete.  You should browse it next.
+       box = Textbox(editwin)
 
-If you're in doubt about the detailed behavior of any of the ncurses entry
-points, consult the manual pages for your curses implementation, whether it's
-ncurses or a proprietary Unix vendor's.  The manual pages will document any
-quirks, and provide complete lists of all the functions, attributes, and
-:const:`ACS_\*` characters available to you.
+       # Let the user edit until Ctrl-G is struck.
+       box.edit()
 
-Because the curses API is so large, some functions aren't supported in the
-Python interface, not because they're difficult to implement, but because no one
-has needed them yet.  Feel free to add them and then submit a patch.  Also, we
-don't yet have support for the menu library associated with
-ncurses; feel free to add that.
+       # Get resulting contents
+       message = box.gather()
 
-If you write an interesting little program, feel free to contribute it as
-another demo.  We can always use more of them!
+See the library documentation on :mod:`curses.textpad` for more details.
 
-The ncurses FAQ: http://invisible-island.net/ncurses/ncurses.faq.html
 
+For More Information
+====================
+
+This HOWTO doesn't cover some advanced topics, such as reading the
+contents of the screen or capturing mouse events from an xterm
+instance, but the Python library page for the :mod:`curses` module is now
+reasonably complete.  You should browse it next.
+
+If you're in doubt about the detailed behavior of the curses
+functions, consult the manual pages for your curses implementation,
+whether it's ncurses or a proprietary Unix vendor's.  The manual pages
+will document any quirks, and provide complete lists of all the
+functions, attributes, and :const:`ACS_\*` characters available to
+you.
+
+Because the curses API is so large, some functions aren't supported in
+the Python interface.  Often this isn't because they're difficult to
+implement, but because no one has needed them yet.  Also, Python
+doesn't yet support the menu library associated with ncurses.
+Patches adding support for these would be welcome; see
+`the Python Developer's Guide <http://docs.python.org/devguide/>`_ to
+learn more about submitting patches to Python.
+
+* `Writing Programs with NCURSES <http://invisible-island.net/ncurses/ncurses-intro.html>`_:
+  a lengthy tutorial for C programmers.
+* `The ncurses man page <http://www.linuxmanpages.com/man3/ncurses.3x.php>`_
+* `The ncurses FAQ <http://invisible-island.net/ncurses/ncurses.faq.html>`_
+* `"Use curses... don't swear" <http://www.youtube.com/watch?v=eN1eZtjLEnU>`_:
+  video of a PyCon 2013 talk on controlling terminals using curses or Urwid.
+* `"Console Applications with Urwid" <http://www.pyvideo.org/video/1568/console-applications-with-urwid>`_:
+  video of a PyCon CA 2012 talk demonstrating some applications written using
+  Urwid.