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CS 101 – Oct. 15 • Common elements in solutions – – – – Types of variables Traversing values in a list Assigning vs. checking if equal Printing things on the same line • Examples and practice Variables • Python loves variables. And Python understands that a variable can be used for different purposes: – Number (both integer and real) – Text – True or False radius = 2.5 name = “Martha” leap = True • Caution: if you want to divide two numbers, you should use real numbers. For example, one-third should be 1.0/3.0 because 1/3 is dividing integers, which equals 0. Traversing a list • We want to visit each element. Two ways to do this: L = [ 5, 4, 7, 3, 2, 6, 1] for number in L: print L for i in range (0, 7): print L[i] = versus == • In Python (and other languages), we need to distinguish between: – Assigning a value to a variable: – Asking if two quantities are equal For example, if hours == 40: overtime = False x=5 x == 5 Output • The “print” statement is designed to display a line of text, and then go on to the next line. Sometimes we want to continue output on the same line. • Two approaches – Put comma at end of statement print “$ ”, – Tell Python you want to print several things. However, if you are printing both text and numbers, you need to put str( ) around the number. – See list.py example. Examples • Ask the user for the length and width of a rectangle. Output the area and perimeter. • Ask the user what 7+5 is. Tell user if the answer is correct or not. • Count how many numbers in a list equal 5. Rectangle # rectangle.py # Find area and perimeter of user’s rectangle. length = input(“What is the length?”) width = input(“What is the width?”) area = length * width perimeter = 2 * (length + width) print "The area is " + str(area) print "The perimeter is " + str(perimeter) User Quiz # quiz.py # See if the user knows what 7+5 is. answer = input(“What is 7 plus 5?”) if answer == 12: print "Good job!" else: print "Sorry, that’s not correct." Count the 5’s # count5.py # Count the 5’s in a list L = [ 5, 4, 2, 5, 1, 2, 5 ] fives = 0 for number in L: if number == 5: fives = fives + 1 print "I found " + str(fives) + " fives."