1. Count Controlled Loops Look at the little children … Why is the sun’s face features orange …

2. Warm Up Practice  Write a program that continually asks the user for a price value  When the user enters the word “end” you should end the program and add the total price of all the products  In addition, display the highest priced item and the lowest priced item

3. Count Controlled Loops  Previously, we learned the “while” loop, which we defined as the condition controlled loop  It is so called “condition controlled” because it iterates the number of times in which a Boolean expression holds True  Today, we will look at what is called a “count controlled” loop

4. Count Controlled Loops  It is called “count controlled” because it iterates a specific number of times  It is not dependent on the truth value of a Boolean expression, or condition

5. Count Controlled Loop  Now, it’s important to remember that a lot of times in Python, we can accomplish the same tasks with various different methods i.e. ELIF’s versus nested IF’s  In the same way, a count controlled loop can be created by using a “while” loop  These various methods are really for convenience’s sake (We should also note that a while loop can be duplicated by a function controlled loop)

6. Count Controlled Loop Example: counter = 0 while counter < 5: print (“this will print 5 times!”) counter +=1

7. Lists  Python has such things called “lists”  Lists are denoted by brackets [ a, b, c, d ] and each item in the list is separated by commas  Lists can be stored and named as variables Example: x = [a, b, c, d]

8. Lists  One important thing to note about lists is that they can hold various data types all at once Example: list = [“name”, “word”, 1, 2, 3]

9. The ‘’for’’ loop  The “for” loop is Python’s native count controlled loop Example: for num in [1, 2, 3, 4, 5]: print(“this will also print 5 times”)

10. The ‘’for’’ loop  The “for” keyword starts the loop  The “num” is the name of the target variable  “in” is another keyword  [1, 2, 3, 4, 5] is the list of items to iterate over  Note the indentation

11. The ‘’for’’ loop  The “for” loop will iterate once for each item in the list passed to it when the loop begins  During the first iteration, the target variable will assume the value of the first item in the list  During the second iteration, it will assume the second item in the list  This continues until you reach the end of the list

12. The ‘’for’’ loop for x in [1, 2, 3, 4, 5]: >> 1 print (x) 2 3 4 5

13. The ‘’for’’ loop for name in [“Josh”, “Jeen”, “Nicole”]: print(“My favorite student is”, name) >> My favorite student is Josh My favorite student is Jeen My favorite student is Nicole

14. Practice – Make Dat DOE  Write a program that asks the user how much money they made from Monday to Sunday  The program should specify the day each time it asks the user for a value  Then sum up the total amount they made and print out

15. Practice – Mechanics  Rewrite the following loop as a “while” loop: for x in [10, 20, 30, 40]: print (x)

16. The range( ) Function  So far, we’ve been TIRELESSLY writing out lists of pre-defined values in our “for” loops  The range( ) function allows us to dynamically generate lists based on pre-determined criteria

17. The range( ) Function for x in range(5): >> iteration # 0 print(“iteration #”, x) iteration # 1 iteration # 2 iteration # 3 iteration # 4

18. The range( ) Function  The range( ) function takes at least one argument  In it’s simplest form, it takes a single integer  The range( ) function returns what we can think of as a list in Python  When passed a single integer, it will return a list of integers from 0 to the number specific minus one

19. The range( ) Function range(5) [ 0, 1, 2, 3, 4] range (10) [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

20. The range( ) Function  However, the range( ) function can behave in different ways  It can take two arguments, which sets a start and an end value  By default, the function increments by 1 range (1, 5) [ 1, 2, 3, 4] range (5, 10) [ 5, 6, 7, 8, 9]

21. The range( ) Function  You can also pass three arguments and set a start value, an end value, and a step value range(0, 10, 2) [0, 2, 4, 6, 8] range(1, 15, 3) [1, 4, 7, 10, 13]  If the step count does not perfectly fall on the end value, it will just include the number before the end value is reached

22. The range( ) Function  Lastly, you can ask the range( ) function to count backwards by passing in a negative step count

23. Practice – Countdown  Write a program that counts down from 10 and then print out “HAPPY NEW YEAR!”

24. Import ‘’time’’  We’ll talk more about this later, but another module we can import into Python is “time”  We can ask Python to pause (for dramatic effect) by calling the sleep( ) function in time  The sleep( ) function can take one argument, denoting the number of seconds to “sleep” **sleep( ) can also take floats

25. Import ‘’time’’ import time for x in range(10, 0, -1): print(x) time.sleep(1) print(“HAPPY NEW YEAR!”)

26. Loop Targets  In a “for” loop, we generally use the target variable as a reference value for some kind of calculation  Remember that the value of the target variable changes with each iteration of the loop

27. Practice – Squares  Write a program that calculates the square of the numbers between 1 and 10  Print out the number and it’s square as your loop iterates

28. Practice – Stair Master  Write a program that prints out the following: ** (2 stars) **** (4 stars) ****** (6 stars) ******** (8 stars) ********** (10 stars) ************ (12 stars)

29. Practice – Divisibility  Write a program that asks the user for an integer  Then print out all numbers that are divisible by that number from 1 to 1,000

30. Practice – Divisibility (extension)  Extend your divisibility program to check for all integers from 1 to 10,000 that are divisible by two different integers simultaneously  Print out 10 numbers per line

31. User Controlled Ranges  Sometimes, we need to ask the user to control the # of iterations within a loop  You can do this by substituting a variable within the range( ) function to control the start, end, and step values of the list that will be generated

32. User Controlled Ranges x = int(input(“start value: “)) y = int(input(“end value: “)) z = int(input(“step value: “)) range(x, y, z)

33. User Controlled Ranges  We can also just put the input( ) function directly into the range( ) function  However, we must remember to convert it into an integer

34. User Controlled Ranges range(int(input(“start: “)), int(input(“end: “)), int(input(“step: “)))  Just be careful, as this can be confusing and you need to keep count of how many parentheses you use