Keyboard

The built-in function input() (or raw_input()) is pretty good for a basic game:

name = input("What is your name? ")
if sum(map(ord, name)) % 2:
    print(f"{name}?! What a beautiful name!")
else:
    print(f"How interesting, {name} you say?")

But it has drawbacks – it’s no good for interactive apps! This function will not return until the return key is pressed, so we can’t do any exciting animations, and we can’t understand or detect arrow keys and others required to make awesome, interactive apps and games!

Blessed fixes this issue with a context manager, cbreak(), and a single function for all keyboard input, inkey().

inkey()

Let’s just dive right into a rich “event loop”, that awaits a keypress for 3 seconds and tells us what key we pressed.

print(f"{term.home}{term.black_on_skyblue}{term.clear}")
print("press 'q' to quit.")
with term.cbreak():
    val = ''
    while val.lower() != 'q':
        val = term.inkey(timeout=3)
        if not val:
           print("It sure is quiet in here ...")
        elif val.is_sequence:
           print("got sequence: {0}.".format((str(val), val.name, val.code)))
        elif val:
           print("got {0}.".format(val))
    print(f'bye!{term.normal}')

cbreak() enters a special mode that ensures os.read() on an input stream will return as soon as input is available, as explained in cbreak(3). This mode is combined with inkey() to decode multibyte sequences, such as \0x1bOA, into a unicode-derived Keystroke instance.

The Keystroke returned by inkey() is unicode – it may be printed, joined with, or compared to any other unicode strings. It also has these special attributes:

• is_sequence (bool): Whether it is an “application” key.

• code (int): The keycode, for equality testing.

• name (str): a human-readable name of any “application” key.

Keycodes

When the is_sequence property tests True, the value of code represents a unique application key of the keyboard.

code may then be compared with attributes of Terminal, which are duplicated from those found in curses(3), or those constants in curses beginning with phrase KEY_, as follows:

All Terminal class attribute Keyboard codes, by name

Name	Value	Example Sequence(s)
KEY_BACKSPACE	263	‘\x08’, ‘\x7f’
KEY_BEGIN	354
KEY_BTAB	353
KEY_C1	351
KEY_C3	352
KEY_CANCEL	355
KEY_CATAB	342
KEY_CENTER	350
KEY_CLEAR	333
KEY_CLOSE	356
KEY_COMMAND	357
KEY_COPY	358
KEY_CREATE	359
KEY_CTAB	341
KEY_DELETE	330	‘\x1b[3~’
KEY_DL	328
KEY_DOWN	258	‘\x1b[B’, ‘\x1b[OB’
KEY_EIC	332
KEY_END	360	‘\x1b[F’, ‘\x1b[K’, ‘\x1b[8~’, ‘\x1b[OF’
KEY_ENTER	343	‘\n’, ‘\r’, ‘\x1bOM’
KEY_EOL	335
KEY_EOS	334
KEY_ESCAPE	361	‘\x1b’
KEY_F0	264
KEY_F1	265	‘\x1bOP’
KEY_F10	274
KEY_F11	275
KEY_F12	276
KEY_F13	277
KEY_F14	278
KEY_F15	279
KEY_F16	280
KEY_F17	281
KEY_F18	282
KEY_F19	283
KEY_F2	266	‘\x1bOQ’
KEY_F20	284
KEY_F21	285
KEY_F22	286
KEY_F23	287
KEY_F3	267	‘\x1bOR’
KEY_F4	268	‘\x1bOS’
KEY_F5	269
KEY_F6	270
KEY_F7	271
KEY_F8	272
KEY_F9	273
KEY_FIND	362	‘\x1b[1~’
KEY_HELP	363
KEY_HOME	262	‘\x1b[H’, ‘\x1b[7~’, ‘\x1b[OH’
KEY_IL	329
KEY_INSERT	331	‘\x1b[2~’
KEY_KP_0	520	‘\x1bOp’
KEY_KP_1	521	‘\x1bOq’
KEY_KP_2	522	‘\x1bOr’
KEY_KP_3	523	‘\x1bOs’
KEY_KP_4	524	‘\x1bOt’
KEY_KP_5	525	‘\x1bOu’
KEY_KP_6	526	‘\x1bOv’
KEY_KP_7	527	‘\x1bOw’
KEY_KP_8	528	‘\x1bOx’
KEY_KP_9	529	‘\x1bOy’
KEY_KP_ADD	514	‘\x1bOk’
KEY_KP_DECIMAL	517	‘\x1bOn’
KEY_KP_DIVIDE	518	‘\x1bOo’
KEY_KP_EQUAL	519	‘\x1bOX’
KEY_KP_MULTIPLY	513	‘\x1bOj’
KEY_KP_SEPARATOR	515	‘\x1bOl’
KEY_KP_SUBTRACT	516	‘\x1bOm’
KEY_LEFT	260	‘\x1b[D’, ‘\x1b[OD’
KEY_LL	347
KEY_MARK	364
KEY_MAX	511
KEY_MESSAGE	365
KEY_MIN	257
KEY_MOUSE	409
KEY_MOVE	366
KEY_NEXT	367
KEY_OPEN	368
KEY_OPTIONS	369
KEY_PGDOWN	338	‘\x1b[U’, ‘\x1b[6~’
KEY_PGUP	339	‘\x1b[V’, ‘\x1b[5~’
KEY_PREVIOUS	370
KEY_PRINT	346
KEY_REDO	371
KEY_REFERENCE	372
KEY_REFRESH	373
KEY_REPLACE	374
KEY_RESET	345
KEY_RESIZE	410
KEY_RESTART	375
KEY_RESUME	376
KEY_RIGHT	261	‘\x1b[C’, ‘\x1b[OC’
KEY_SAVE	377
KEY_SBEG	378
KEY_SCANCEL	379
KEY_SCOMMAND	380
KEY_SCOPY	381
KEY_SCREATE	382
KEY_SDC	383
KEY_SDL	384
KEY_SDOWN	336	‘\x1b[1;2B’
KEY_SELECT	385	‘\x1b[4~’
KEY_SEND	386
KEY_SEOL	387
KEY_SEXIT	388
KEY_SFIND	389
KEY_SHELP	390
KEY_SHOME	391
KEY_SIC	392
KEY_SLEFT	393	‘\x1b[1;2D’
KEY_SMESSAGE	394
KEY_SMOVE	395
KEY_SNEXT	396
KEY_SOPTIONS	397
KEY_SPREVIOUS	398
KEY_SPRINT	399
KEY_SREDO	400
KEY_SREPLACE	401
KEY_SRESET	344
KEY_SRIGHT	402	‘\x1b[1;2C’
KEY_SRSUME	403
KEY_SSAVE	404
KEY_SSUSPEND	405
KEY_STAB	340
KEY_SUNDO	406
KEY_SUP	337	‘\x1b[1;2A’
KEY_SUSPEND	407
KEY_TAB	512	‘\t’
KEY_UNDO	408
KEY_UP	259	‘\x1b[A’, ‘\x1b[OA’
KEY_UP_LEFT	348
KEY_UP_RIGHT	349

All such keystrokes can be decoded by blessed, there is a demonstration program, keymatrix.py that tests how many of them you can find !

delete

Typically, backspace is ^H (8, or 0x08) and delete is ^? (127, or 0x7f).

On some systems however, the key for backspace is actually labeled and transmitted as “delete”, though its function in the operating system behaves just as backspace. Blessed usually returns “backspace” in most situations.

It is highly recommend to accept both KEY_DELETE and KEY_BACKSPACE as having the same meaning except when implementing full screen editors, and provide a choice to enable the delete mode by configuration.

Alt/meta

Programs with GNU readline, like bash, have Alt combinators, such as ALT+u to uppercase the word after cursor. This is achieved by the configuration option altSendsEscape or metaSendsEscape in xterm.

The default for most terminals, however, is for this key to be bound by the operating system, or, used for inserting international keys, (where the combination ALT+u, a is used to insert the character ä).

It is therefore a recommendation to avoid alt or meta keys entirely in applications.

And instead prefer the ctrl-key combinations, maybe along with raw(), to avoid instructing users to custom-configure their terminal emulators to communicate Alt sequences.

If you still wish to optionall decode them, ALT+z becomes Escape + z (or, in raw form \x1bz). This is detected by blessings as two keystrokes, KEY_ESCAPE and 'z'. Blessings currently provides no further assistance in detecting these key combinations.