Using Forms and Python

While it’s nice to click buttons in an adventure game to work your way through the story, most applications need more powerful and flexible means of capturing user input. These usually involve forms containing various different types of input. Happily, PyperCard has a very simple form mechanism that allows you to specify just one input type per card.

In addition, you don’t need to use JSON to specify your cards (although this is often convenient for applications that don’t use forms). It’s possible to specify cards using Python and define how to handle the user input and other changes in the application’s state by creating simple functions.

Defining a card in Python is very simple:

from pypercard import CardApp, Card

hello_card = Card(
    buttons=[{"label": "Finish", "target": "goodbye"}]

goodbye_card = Card(
    buttons=[{"label": "Start again", "target": "hello"}]

Note how the buttons are defined as Python dictionaries.

Adding cards to an app is as simple as putting them into a Python list and passing them into the application:

stack = [hello_card, goodbye_card, ]
app = CardApp(stack=stack)

Alternatively, you can add cards individually via the application’s add_card method:

app = CardApp()

When a card or stack of cards are added to the application, the card titles will be checked to ensure they are unique. If not, PyperCard will raise an exception.

There are some further attributes which PyperCard cards can have which have not been mentioned so far. They are:

  • text_size - the size of the text. Expressed as a number. If not given, defaults to 48.
  • form - the type of input to display on the card (see below). If not given, no form input is displayed.
  • options - options which define the form input’s behaviour (see below). Ignored if no form attribute is given.
  • auto_advance - a number (e.g. 3.5) to indicate the number of seconds to wait before automatically transitioning to a target card. If not given, the card won’t automatically transition. You must supply a valid auto_target attribute, or the card will appear paused.
  • auto_target - a string identifying the target card to automatically transition to after auto_advance seconds.

In addition to the required label and target attributes, buttons may also have the following optional attributes:

  • text_size - the size of the text in the button’s label. Expressed as a number. If not given defaults to 24.
  • text_color - the colour of the text in the button’s label (e.g. "red"). If not given, defaults to "white".
  • background_color - the colour of the button’s background (e.g. "blue"). If not given, defaults to "grey".

Form Inputs

For an application to be useful it often needs to gather and process user input. In PyperCard this is achieved through form input fields. Each card may only have one form input field.

There are five possible types of input.

A single-line text box:


A multi-line text entry field:


A multiple choice field so users can select none, one or more of a range of values:


A selector field so users can select a single value or no value at all from a range of values:


A slider for providing numeric input between a minimum and maximum value with an option to define the step between values as the slider moves.


Function follows Form

Always Check User Input!

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