Input

Input objects provide user keypress events and other control events.

Input - Example

>>> from curtsies import Input
>>> with Input(keynames='curtsies') as input_generator:
...     for e in Input():
...         if e in (u'<ESC>', u'<Ctrl-d>'):
...             break
...         else:
...             print(e)

Input - Getting Keyboard Events

The simplest way to use an Input object is to iterate over it in a for loop: each time a keypress is detected or other event occurs, an event is produced and can be acted upon. Since it’s iterable, next() can be used to wait for a single event. send() works like next() but takes a timeout in seconds, which if reached will cause None to be returned signalling that no keypress or other event occured within the timeout.

Key events are unicode strings, but sometimes event objects (see Event) are returned instead. Built-in events signal SigIntEvent events from the OS and PasteEvent consisting of multiple keypress events if reporting of these types of events was enabled in instantiation of the Input object.

Input - Using as a Reactor

Custom events can also be scheduled to be returned from Input with callback functions created by the event trigger methods.

Each of these methods returns a callback that will schedule an instance of the desired event type:

  • Using a callback created by event_trigger() schedules an event to be returned the next time an event is requested, but not if an event has already been requested (if called from another thread).
  • threadsafe_event_trigger() does the same, but may notify a concurrent request for an event so that the custom event is immediately returned.
  • scheduled_event_trigger() schedules an event to be returned at some point in the future.

Input - Context

next() and send() must be used within the context of that Input object.

Within the (context-manager) context of an Input generator, an in-stream is put in raw mode or cbreak mode, and keypresses are stored to be reported later. Original tty attributes are recorded to be restored on exiting the context. The SigInt signal handler may be replaced if this behavior was specified on creation of the Input object.

Input - Notes

Input takes an optional argument keynames for how to name keypress events, which is 'curtsies' by default. For compatibility with curses code, you can use 'curses' names, but note that curses doesn’t have nice key names for many key combinations so you’ll be putting up with names like u'\xe1' for option-j and '\x86' for ctrl-option-f. Pass 'plain' for this parameter to return a simple unicode representation.

PasteEvent objects representing multiple keystrokes in very rapid succession (typically because the user pasted in text, but possibly because they typed two keys simultaneously). How many bytes must occur together to trigger such an event is customizable via the paste_threshold argument to the Input object - by default it’s one greater than the maximum possible keypress length in bytes.

If sigint_event=True is passed to Input, SIGINT signals from the operating system (which usually raise a KeyboardInterrupt exception) will be returned as SigIntEvent instances.

To set a timeout on the blocking get, treat it like a generator and call .send(timeout). The call will return None if no event is available.

Input - Events

To see what a given keypress is called (what unicode string is returned by Terminal.next()), try python -m curtsies.events and play around. Events returned by Input fall into two categories: instances of subclasses of Event and Keypress strings.

Input - Event Objects

class curtsies.events.Event
class curtsies.events.SigIntEvent

Event signifying a SIGINT

class curtsies.events.PasteEvent

Multiple keypress events combined, likely from copy/paste.

The events attribute contains a list of keypress event strings.

class curtsies.events.ScheduledEvent(when)

Event scheduled for a future time.

Parameters:when (float) – unix time in seconds for which this event is scheduled

Custom events that occur at a specific time in the future should be subclassed from ScheduledEvent.

Input - Keypress Strings

Keypress events are Unicode strings in both Python 2 and 3 like:

  • a, 4, *, ?
  • <UP>, <DOWN>, <RIGHT>, <LEFT>
  • <SPACE>, <TAB>, <F1>, <F12>
  • <BACKSPACE>, <HOME>, <PADENTER>, <PADDELETE>
  • <Ctrl+a>, <Ctrl+SPACE>
  • A, <Shift-TAB>, ?
  • <Esc+a>, <Esc+A>, <Esc+Ctrl-A>
  • <Esc+Ctrl+A>
  • <Meta-J>, <Meta-Ctrl-J> (this is old-style meta)

Likely points of confusion for keypress strings:

  • Enter is <Ctrl-j>
  • Modern meta (the escape-prepending version) key is <Esc+a> while control and shift keys are <Ctrl-a> (note the + vs -)
  • Letter keys are capitalized in <Esc+Ctrl-A> while they are lowercase in <Ctrl-a> (this should be fixed in the next api-breaking release)
  • Some special characters lose their special names when used with modifier keys, for example: <TAB>, <Shift-TAB>, <Esc+Ctrl-Y>, <Esc+Ctrl-I> are all produced by the tab key, while y, Y, <Shift-TAB>, <Esc+y>, <Esc+Y>, <Esc+Ctrl-y>, <Esc+Ctrl-Y>, <Ctrl-Y> are all produced by the y key. (This should really be figured out)

Input - API docs

class curtsies.Input(in_stream=None, keynames='curtsies', paste_threshold=8, sigint_event=False)

Keypress and control event generator

Returns an Input instance.

Parameters:
  • in_stream (file) – Defaults to sys.__stdin__
  • keynames (string) – How keypresses should be named - one of ‘curtsies’, ‘curses’, or ‘plain’.
  • paste_threshold (int) – How many bytes must be read in one os.read on the in_stream to trigger the keypresses they represent to be combined into a single paste event
  • sigint_event (bool) – Whether SIGINT signals from the OS should be intercepted and returned as SigIntEvent objects
unget_bytes(string)

Adds bytes to be internal buffer to be read

This method is for reporting bytes from an in_stream read not initiated by this Input object

send(timeout=None)

Returns an event or None if no events occur before timeout.

event_trigger(event_type)

Returns a callback that creates events.

Returned callback function will add an event of type event_type to a queue which will be checked the next time an event is requested.

scheduled_event_trigger(event_type)

Returns a callback that schedules events for the future.

Returned callback function will add an event of type event_type to a queue which will be checked the next time an event is requested.

threadsafe_event_trigger(event_type)

Returns a callback to creates events, interrupting current event requests.

Returned callback function will create an event of type event_type which will interrupt an event request if one is concurrently occuring, otherwise adding the event to a queue that will be checked on the next event request.