Key Input
=========

This section deals with single or combined keypress input.  For input involving typing longer strings, see :doc:`Text Input<textinput>`.

See :ref:`Event Handling` for a discussion of the basics of dealing with input.

Jupyter notebook limitation: Key events are swallowed by the Jupyter notebook as part of the user interface and are not available to a VPython program.

What Keys are Down?
-------------------

More than one key may be down at once.  The ``keysdown()`` function provides a list of all keys that are currently down.

..	py:function:: mykeys = keysdown()  # a list of keys

Keynames include:

* single characters for alphanumeric keys, e.g. 'b'
* function keys 'f1' through 'f10'
* 'backspace'
* 'caps lock'
* 'tab'
* 'shift'
* 'ctrl'
* 'alt'
* 'pageup'
* 'pagedown'
* 'end'
* 'home'
* 'left'  (left arrow)
* 'right' (right arrow)
* 'down'  (down arrow)
* 'up'  (up arrow)
* 'insert'
* 'delete'
* 'break'  

Typing into a Label
^^^^^^^^^^^^^^^^^^^

The ``input()`` and ``winput()`` commands allow the processing of longer user input.

The test routine below lets the user type text one character at a time into a label:

..	code-block::

    prose = label() # initially blank text

    def keyInput(evt):
        s = evt.key
        if len(s) == 1: # includes enter ('\n')
            prose.text += s # append new character
        elif ( s == 'delete' or s is 'backspace' ) and len(prose.text) > 0:
            prose.text = prose.text[:-1] # erase letter

    scene.bind('keydown', keyInput)


.. include:: ./eventseealso.rst