Lecture 15 Slides - Review + Events and Listeners

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Listening for Inputs

CS 110

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Reminders and Announcements

  1. Ex 5 due tonight (hints available on edSTEM!)
  2. We'll talk about P1 on Monday (due in two Fridays)
    1. Ex6 will ask you to complete the first half of P1

Next Week

  • Monday - Short Circuiting Loops
  • Wednesday - Keyboard Events + Scope (Pre-Recorded + MQ 10) + Tutorial 5
  • Friday - Using Loops for Data + MQ 11
    • Ex 6 due

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quack

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Problem 1: Infinite Loops

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counter = 5

while counter < 5:

print(counter)

counter = counter + 1

The loop never begins (condition starts off as False)

Problem 2: Loops that aren't

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INPUT AND EVENTS

Expanding past just using the Python interpreter

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Examples of Inputs

There are many different kinds of inputs, which should all be very familiar to you:�

  • Clicking a button
  • Dragging, swiping, rotating
  • Using sensors
  • Reading data from files or databases
  • Double-clicking a program to start it

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Events: Ways of Dealing with User Input

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Events allow programs to listen to particular events (clicks, drags, etc.) and execute parts of a program based on the input. Events have two parts:

  1. An event listener, which can detect that an event has occurred and the nature of it. Listeners notify your program that something has happened.
  2. An event handler (the function), which is the block of code that responds to an event when is triggered by executing a code block. Event handlers are sometimes called “callbacks.”

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listen_for("LEFT-CLICK", do_something)

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We use this function to set the listener up.

A function name to run when the event happens (handler) that is defined to have exactly 1 input

Setting an Event Listener on the Pop-up Window

The event to listen for (a special string specified by Python)

Options as of Week 6 (all strings) :

LEFT-CLICK RIGHT-CLICK ALT-CLICK LEFT-DRAG

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Demos

lecture15/event_demos/

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