Random Functional Labels

Announcements

• I’m still working through the PS2 feedback unfortunately
  • It’s been a week, and this problem set takes a while to score
• Don’t forget that the Wordle Project is posted when you want to get a start on that
  • Please don’t wait until late next week to start it
• My availability today is almost non-existant, but I’ll be around for 30 min after class or after 5pm
• Visiting Faculty Candidate today!
  • Teaching Demonstration at noon (this room)
  • Research Talk at 1 (this room)
• Polling: rembold-class.ddns.net

Smile!

gw = GWindow(400, 400)

head = GOval(20, 20, 360, 360)
head.set_fill_color("yellow")
head.set_filled(True)
gw.add(head)

reye = GOval(110, 100, 40, 40)
reye.set_filled(True)
gw.add(reye)

leye = GOval(250, 100, 40, 40)
leye.set_filled(True)
gw.add(leye)

mouth = GLine(150, 250, 250, 250)
mouth.set_line_width(5)
gw.add(mouth)

Review Question

Which of the below images would be produced by the following code?

gw = GWindow(200,200)
for c in range(0,10):
    for r in range(0,10):
        rect = GRect(20*c,20*r,20,20)
        if (r+c) % 2 != 0:
            rect.set_filled(True)
    gw.add(rect)

Label It!

• Sometimes you need to add some text to the window

• Can display any string using GLabel using the following format:

  msg = GLabel(string_to_add, x_location, y_location)

• Here string_to_add is the text you want to display, and x_location and y_location are the (x,y) coordinates of where you want to place the origin of the label.

Label Geometry

Interacting with Labels

Label Example

gw = GWindow(500, 200)
msg = GLabel("hello world!", 50, 100)
msg.set_font("italic bold 80px 'times new roman'")
gw.add(msg)

Centering a GLabel

Centering Example

gw = GWindow(500, 200)
msg = GLabel("hello world!")
msg.set_font("italic bold 20px 'times new roman'")
x = gw.get_width()  / 2 - msg.get_width()  / 2
y = gw.get_height() / 2 + msg.get_ascent() / 2
gw.add(msg, x, y)

Nondeterministic Programming

• For Wordle, the game is only interesting if the secret word is not the same every time!
• Let’s look at the built-in random library, which lets us simulate random processes
• Programs that involve random processes that cannot be predicted in advance are said to be nondeterministic
• Nondeterministic behavior is essential to many applications.
  • Many games would not be enjoyable if they behaved the exact same way every playthrough
  • Important practical uses in simulations, computer security, and algorithm research

Important Functions in random

Random Examples

import random

def random_redblue():
    if random.random() > 0.5:
        return "red"
    else:
        return "blue"

def random_color():
    color_string = "#"
    for i in range(6):
        color_string += random.choice("0123456789ABCDEF")
    return color

Function Review

• A function is just a sequence of statements that have been collected together and given a name
  • Makes it possible to execute the statements multiple times much more easily
• Some reminders about vocabulary:
  • Invoking or running a function by name is known as calling that function.
  • The caller passes information to a function using arguments.
  • When a function completes its block of code, it returns to its caller.
  • The function gives information back to the caller by returning a result

def function_name( parameter_list ):
  function_body

Predicate Functions

• Functions that return a Boolean value are called predicate functions

  def is_divisible_by(x, y):
    return x % y == 0

• Once you have defined a predicate function, you can use it in any conditional expression!

  for i in range(1, 100):
    if is_divisible_by(i, 7):
        print(i)

Predicate No-nos

• Don’t complicate your code for no reason!

• Work directly with the boolean values when possible

• Try not to code patterns like the following:

  def is_divisible_by(x, y):
    if x % y == 0:
        return True
    else:
        return False

  for i in range(1, 100):
    if is_divisible_by(i,7) == True:
        print(i)

Parameter Purposes

• Often functions need some sort of outside input in order to be useful
• It is necessary for them to know enough details so that they can carry out the requested task, but not so many that the function becomes annoying to use
  • Imagine you were trying to accomplish the task yourself!
  • What is the minimum amount of information you would need to know?
• The minimum necessary information needed for the function to accomplish its task is generally the information conveyed in the parameters
• There is always a balance
  • More parameters makes your function more general, to be used elsewhere
  • More parameters are tedious and potentially error prone to enter if unnecessary

Jockeying for Position

• So far we have used a positional way to assign arguments to parameters

  >>> def func( first, second, third ):
          print( first, second, third )
  >>> func(1,2,3)
  1 2 3
  >>> func(2,6,4)
  2 6 4

  • First argument to first parameter, second to second parameter, etc

The Word is Key

• Arguments may also be specified by a keyword, in which the caller precedes the argument with a parameter name and equals sign

• Always stores the argument value in the specified parameter

  >>>  def func( first, second, third ):
        print( first, second, third )
  >>>  func(third=4, first=2, second=6)
  2 6 4

• Keyword arguments can appear in any order

• All keyword arguments must come after any positional arguments!