Transcript Compound Statements and Random Numbers

Recap: If, elif, else
If <True condition>:
Do this
Elif <True condition>:
Otherwise, do this
Else:
Do this
Compound Statements and
Random Numbers
Compound Statements
 You can use compound statements to make sure a block will only run if
there is more than one condition to be satisfied
if <condition 1> and <condition 2>
Then do this
Will only run if
both conditions
are true
if <condition 1> or <condition 2>
Then do this
Will only run if at
least one
condition is true
When you’re finished…
How could you make your program start over again and
re-prompt the user if the user put in a negative number
Add this to your existing code and email me .py file at
[email protected] and turn in your grade sheet
Read about random numbers and the random module:
pages 50-53
Creating while loops
 While some condition is true, repeat something
 In coding: you might want to create a quiz show game, while there
are questions left, keep playing the game.
 The while loops lets you do this
What’s a while loop
 Runs while a certain condition is true
Examples:
number = int(input("enter a number"))
while number !=5
number = int(input(“Guess another number”))
Generating Random Numbers
As much as users want consistent, predictable results from
programs, sometimes what make the programs exciting is
their unpredictability
Random numbers can supply an element of surprise
Python makes it easy to generate those random numbers
Python generates random numbers based on a formula, so
they are not truly random.
This kind of random generation is called pseudorandom
Introducing the Craps Roller Program
 Open the Craps Roller Program from the Chapter 3 Folder
 Craps Roller replicated the dice roll of the fast-paced, casino game
of craps. You don’t have to know anything about craps to
appreciate the program.
 Craps Roller just simulates the roll of two, six-sided dice. It displayed
the value of each and their total.
 To determine the dice values, the program uses functions that
generates random number. Figure 3.2 shows the program
Importing the random Module
The first line of code in the program introduces the
import statement
The statement allows you to import, or load,
modules, in this case, the random module:
import random
Modules
 Modules are files that contain code meant to be used in other
programs. These modules usually group together a collection of
programming related to one area. The random module contains
functions related to generating random numbers and producing
random results.
 When you import a module, it was either installed as part of your
Python installation, or was downloaded and installed later on, prior
to your running the program that imports it.
Generating Random Numbers
You can generate random numbers using:
 randint()
randrange()
randint() Function
Produces a random integer
Notice the program doesn’t directly call randint()
It calls the function:
random.randint(1,6)
This accesses the function randint() through its module,
random
Dot notation
 You can call a function from an imported module by giving the
module name, followed by a period, followed by the function call
itself (similar to string methods).
 This method of action is called dot notation.
 Using dot notation random.randint() means the function
randint() that belongs to the module random.
 Dot notation can be used to access different elements of imported
modules
randint() function
Requires two integer argument values and returns a
random integer between those two values, which may
include either of the argument values.
 By passing the values 1 and 6 to the function, you are
guaranteed to get back either 1,2,3,4,5 or 6
randrange() function
produces a random integer
Use a single, positive integer argument
The function returns a random integer from, and
including, 0, up to, but not including, that number
Example: random.randrange(6) produces either a
0,1,2,3,4, or 5
Where’s the 6 in the Craps Rollar?
 randrange(6) is picking a random number from a group of 6
numbers – and the list starts with 0
 If you add 1 to the result to get the right value for a die2:
 die2=random.randrange(6)+1
As a result, die 2 gets either a 1,2,3,4,5, or 6.
Research:
What if you want to pick a random string out of a
list? What function would you use in python? Do
some research and turn in your answer.