Tools

There are some tools provided with PiFace Control and Display which simplify getting input from a user.

Question

pifacecad.tools.question.LCDQuestion will display a question on the top row and an answer on the bottom. The user can cycle through answers by moving the navigation switch left and right and select an answer by pressing the navigation switch in.

It can be used like this:

>>> import pifacecad
>>> from pifacecad.tools.question import LCDQuestion

>>> question = LCDQuestion(question="What is 5 x 2?", answers=["1", "10", "12"])
>>> answer_index = question.ask()

You can pass in an already initialised Control and Display object and also specify a custom selector:

>>> import pifacecad
>>> from pifacecad.tools.question import LCDQuestion

>>> customcad = pifacecad.PiFaceCAD()
>>> customcad.lcd.cursor_off()
>>> customcad.lcd.blink_off()

>>> question = LCDQuestion(question="What is 5 x 2?",
...                        answers=["1", "10", "12"],
...                        selector="#",
...                        cad=customcad)
>>> answer_index = question.ask()

Scanf

pifacecad.tools.scanf.LCDScanf will display a custom string that can be modified using the navigation switch. In ‘select’ mode, moving the navigation switch left or right (switches 6 and 7) selects a character. Change to ‘edit’ mode by pressing the navigation switch in (switch 5). In edit mode, moving the navigation switch left or right changes the character.

To return the input, move the cursor under the ‘enter’ arrow and press the navigation switch in.

The LCDScanf class can be used like this:

>>> import pifacecad
>>> from pifacecad.tools.scanf import LCDScanf

>>> scanner = LCDScanf("Text: %c%2i%.%r")
>>> print(scanner.scan())  # user enters things on PiFace C&D
['a', '13', '!']

The format string defines editable variables using a % symbol. The format specification is:

c: Characters
C: Capital Characters
i: Integers
d: Integers
x: Hexadecimal
X: Capital Hexadecimal
.: Punctuation
m: Custom (specifed by ``custom_values`` in init args)
r: Return (switch 5 to submit string)

To add multiple characters in the same variable you can specify a number after the % symbol. For example, to request that the user enter a two digit integer:

>>> print(LCDScanf("%2i%r").scan())
['42']

You can use the m specifier to enter custom variable values:

>>> scanner = LCDScanf("Animal: %m%r", custom_values=('cat', 'dog', 'fish'))
>>> print(scanner.scan())
['fish']