# for loops

for num in range(1, 100, 5):
    print("(step by 5) num " + str(num) + " is odd ? " + str(num % 2 == 1))

for num in range(1, 10):
    print("num " + str(num) + " is odd ? " + str(num % 2 == 1))


for num in range(10, 20):  #to iterate between 10 to 20
    for i in range(2, num): #to iterate on the factors of the number
        if num % i == 0:      #to determine the first factor
            j = num / i          #to calculate the second factor
            print('%d equals %d * %d' % (num, i, j))
            break #to move to the next number, the #first FOR
        else:                  # else part of the loop
            print(num, 'is a prime number')


for letter in 'Python':
    print('Current Letter :', letter)


animals = ['dog', 'cat', 'fish']
for animal in animals:
    print('Current animal :', animal)


print("=== example for loop, using the in keyword and list ===")
## for loop, using the in operator with list
experts = ["wear", "no", "no", "wear", "wear", "no"]
for expert in experts:
    if expert == "wear":
        print("shake")
    else:
        print("no")


print("=== example for loop, using the range operator ===")
## for loop, using the range operator
string1 = "for loop, using range"
string2 = "o"
result = ""
size1 = len(string1)
position = 0
for position in range(0, size1):
    if string1[position] != string2:
        result = result + string1[position]
    position += 1
print("result = " + result)


i = 5
for i in range(5, 0, -1):
   print(i * i * i)



## exercise (for loop using the range operator)
## consider when does the loop stop
number_of_courses = int(input("Enter the number of courses : " ))
for cnt in range(0, number_of_courses):
    letter = ""

    grades = input("Enter 3 exams grade : ")
    list_of_grades = grades.split()

    #print(list_of_grades)
    #print(list_of_grades[0])

    grade_average = (float(list_of_grades[0]) + float(list_of_grades[1]) + float(list_of_grades[2])) / 3

    # determine a letter grade and store it for later use
    if grade_average >= 98:
        letter = "A+"
    elif grade_average >= 93:
        letter = "A"
    elif grade_average >= 90:
        letter = "A-"
    elif grade_average >= 87:
        letter = "B+"
    elif grade_average >= 83:
        letter = "B"
    elif grade_average >= 80:
        letter = "B-"
    elif grade_average >= 77:
        letter = "C+"
    elif grade_average >= 73:
        letter = "C"
    elif grade_average >= 70:
        letter = "C-"
    elif grade_average >= 67:
        letter = "D+"
    elif grade_average >= 63:
        letter = "D"
    elif grade_average >= 60:
        letter = "D-"
    else:
        letter = "F"

    # Why should we use if-elif-elif...  instead of if-if-if..., though both ways work?

    print(format(grade_average, ".3f") + ", " + letter)

    cnt += 1        # why do we need to increment cnt?





##### review slicing
string1 = "for loop, using range"
string2 = "o"


print("result = " + result)