Section 1.15 - IT 140_ Introduction to Scripting _ zyBooks

 Students: Section 1.15 is a part of 1 assignment: 1-3 zyBooks Participation Activities Includes: PA 1.15 Numeric types: Floating-point Floating-point numbers and scienti±c notation A ±oating-point number is a real number, like 98.6, 0.0001, or -666.667. The term "±oating-point" refers to the decimal point being able to appear anywhere ("±oat") in the number. Thus, ±oat is a data type for ±oating-point numbers. A ±oating-point literal is written with the fractional part even if that fraction is 0, as in 1.0, 0.0, or 99.0. Figure 1.15.1: A program using ±oat-type variables. The below program reads in a ±oating-point value from a user and calculates the time to drive and ±y the distance. Note the use of the built-in function ±oat() when reading the input to convert the input string into a ±oat. Note that print handles ±oating-point numbers straightforwardly. miles = float ( input ( 'Enter a distance in miles: ' )) hours_to_fly = miles / 500.0 hours_to_drive = miles / 60.0 print ( miles , 'miles would take:' ) print ( hours_to_fly , 'hours to fly' ) print ( hours_to_drive , 'hours to drive' ) Enter a distance in miles: 450 450.0 miles would take: 0.9 hours to fly 7.5 hours to drive ... Enter a distance in miles: 1800 1800.0 miles would take: 3.6 hours to fly 30.0 hours to drive Scienti²c notation is useful for representing ±oating-point numbers that are much greater than or much less than 0, such as 6.02x10 . A ±oating-point literal using scienti²c notation is written using an e preceding the power-of-10 exponent, as in 6.02e23 to represent 6.02x10 . The e stands for exponent. Likewise, 0.001 is 1x10 , so it can be written as 1.0e-3. PARTICIPATION ACTIVITY 1.15.1: Scienti²c notation. 1) Type 1.0e-4 as a ±oating-point literal but not using scienti²c notation, with a single digit before and four digits after the decimal point. 2) Type 7.2e-4 as a ±oating-point literal but not using scienti²c notation, with a single digit before and ²ve digits after the decimal point. 3) Type 540,000,000 as a ±oating-point literal using scienti²c notation with a single digit before and after the decimal point. 4) Type 0.000001 as a ±oating-point literal using scienti²c notation with a single digit before and after the decimal point. 5) Type 623.596 as a ±oating-point literal using scienti²c notation with a single digit before and ²ve digits after the decimal point. zyDE 1.15.1: Energy to mass conversion. Albert Einstein's equation E = mc is likely the most widely known mathematical formula. The equation describes the mass-energy equivalence, which states that the mass (amount of matter) m of a body is directly related to the amount of energy E of the body, connected via a constant value c , the speed of light squared. The signi²cance of the equation is that matter can be converted to energy, (and theoretically, energy back to matter). The mass-energy equivalence equation can be used to calculate the energy released in nuclear reactions, such Feedback? 23 23 -3 Check Show answer Check Show answer Check Show answer Check Show answer Check Show answer Feedback? 2 2

as nuclear ²ssion or nuclear fusion, which form the basis of modern technologies like nuclear weapons and nuclear power plants. The following program reads in a mass in kilograms and prints the amount of energy stored in the mass. Also printed is the equivalent numbers of AA batteries and tons of TNT. 0.1 Over²ow Float-type objects have a limited range of values that can be represented. For a standard 32-bit installation of Python, the maximum ±oating-point value is approximately 1.8x10 , and the minimum ±oating-point value is 2.3x10 . Assigning a ±oating-point value outside of this range generates an Over±owError . Over±ow occurs when a value is too large to be stored in the memory allocated by the interpreter. For example, the program in the ²gure below tries to store the value 2.0 , which causes an over±ow error. In general, ±oating-point types should be used to represent quantities that are measured, such as distances, temperatures, volumes, and weights, whereas integer types should be used to represent quantities that are counted, such as numbers of cars, students, cities, hours, and minutes. Figure 1.15.2: Float can over±ow. print ( '2.0 to the power of 256 =' , 2.0 ** 256 ) print ( '2.0 to the power of 512 = ' , 2.0 ** 512 ) print ( '2.0 to the power of 1024 = ' , 2.0 ** 1024 ) 2.0 to the power of 256 = 1.15792089237e+77 2.0 to the power of 512 = 1.34078079299e+154 2.0 to the power of 1024 = Traceback (most recent call last): File "<stdin>", line 3, in <module> OverflowError: (34, 'Result too large') PARTICIPATION ACTIVITY 1.15.2: Floating-point versus integer. Choose the right type for a variable to represent each item. 1) The number of cars in a parking lot. ±oat int 2) The current temperature in Celsius. ±oat int 3) A person's height in centimeters. ±oat int 4) The number of hairs on a person's head. ±oat int 5) The average number of kids per household. ±oat int CHALLENGE ACTIVITY 1.15.1: Gallons of paint needed to paint walls. Finish the program to compute how many gallons of paint are needed to cover the given square feet of walls. Assume 1 gallon can cover 350.0 square feet. So gallons = the square feet divided by 350.0. If the input is 250.0, the output should be: 0.714285714286 Load default template... c_meters_per_sec = 299792458 # Speed of light (m/s) joules_per_AA_battery = 4320.5 # Nickel-Cadmium AA batteries joules_per_TNT_ton = 4.184e9 #Read in a floating-point number from the user mass_kg = float ( input ()) #Compute E = mc^2. energy_joules = mass_kg * ( c_meters_per_sec **2) # E = mc^2 print ( 'Total energy released:' , energy_joules , 'Joules' ) #Calculate equivalent number of AA and tons of TNT. num_AA_batteries = energy_joules / joules_per_AA_battery num_TNT_tons = energy_joules / joules_per_TNT_ton print ( 'Which is as much energy as:' ) print ( ' ' , num_AA_batteries , 'AA batteries' ) print ( ' ' , num_TNT_tons , 'tons of TNT' ) Run Feedback? 308 -308 1024 Feedback? Feedback? 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18