#set document(title: "2.2 Type conversion", author: "OpenStax / XYZ Homework") #set page(width: 8.5in, height: auto, margin: 1in) #import "@preview/cetz:0.5.2" #set text(font: ("STIX Two Text", "Libertinus Serif", "New Computer Modern"), size: 10.5pt, lang: "en") #show math.equation: set text(font: ("STIX Two Math", "New Computer Modern Math")) #set par(justify: true, leading: 0.62em, spacing: 0.9em) #set enum(spacing: 1.1em) // room between list items so tall inline fractions don't collide #set list(spacing: 1.1em) #set table(stroke: 0.5pt + rgb("#c7ccd3")) #let BLUE = rgb("#183B6F") // brand navy — section bars + example/solution labels (white on navy 11.09:1) #let ORANGE = rgb("#A94509") // brand primary-700 — AA-safe deep orange for TEXT (5.93:1 on white; raw brand #F37021 is 2.94:1 and must never carry text) #let RED = rgb("#DC2626") // brand error-600 #let GREEN = rgb("#059669") // brand success-600 (decoration only; small green text uses green-text #007942) #show heading.where(level: 1): it => block(width: 100%, above: 0pt, below: 16pt, fill: gradient.linear(BLUE, rgb("#2C5AA0")), inset: (x: 14pt, y: 12pt), radius: 3pt, text(fill: white, weight: "bold", size: 19pt, it.body)) #show heading.where(level: 2): it => block(width: 100%, above: 18pt, below: 10pt, fill: BLUE, inset: (x: 10pt, y: 6pt), radius: 2pt, text(fill: white, weight: "bold", size: 12pt, it.body)) #show heading.where(level: 3): it => text(fill: ORANGE, weight: "bold", size: 12.5pt, it.body) #show heading.where(level: 4): it => text(fill: BLUE, weight: "bold", size: 10.5pt, it.body) #let examplebox(label, title, body) = block(width: 100%, breakable: true, fill: rgb("#EFF1F5"), stroke: 0.5pt + rgb("#CFDDF0"), radius: 4pt, inset: 10pt, above: 12pt, below: 12pt)[ #block(below: 6pt)[#box(fill: BLUE, inset: (x: 6pt, y: 2pt), radius: 2pt, text(fill: white, weight: "bold", size: 8.5pt, label)) #h(0.4em) #strong[#title]] #body] // rail = decorative left rule (raw brand token); labelcolor = AA-safe label text shade #let notebox(label, rail, labelcolor, tint, body) = block(width: 100%, breakable: true, fill: tint, stroke: (left: 3pt + rail), inset: (left: 10pt, rest: 8pt), radius: (right: 4pt), above: 11pt, below: 11pt)[ #text(fill: labelcolor, weight: "bold", size: 7.5pt, tracking: 0.5pt)[#upper(label)] #linebreak() #body] #let solutionbox(body) = block(above: 4pt, below: 8pt)[ #text(fill: BLUE, weight: "bold", size: 8.5pt)[Solution] #linebreak() #body] #let figph(msg) = block(width: 100%, height: 60pt, fill: rgb("#f6f7f9"), stroke: (paint: rgb("#c7ccd3"), dash: "dashed"), radius: 4pt, inset: 10pt)[ #align(center + horizon, text(fill: rgb("#889"), style: "italic", size: 9pt, msg))] // Standardize inlined figure sizes: measure the natural CeTZ canvas, then scale to a // consistent envelope (aspect-aware; see build_typst.py FIG_* constants). Unlike the // print preamble, dimensions are FLOORED: in an editor a user can trim a figure to a // degenerate 1-D shape (a bare line), and w/h or tw/w would then divide by zero. #let _STD_W = 3.5 #let _WIDE_W = 5.6 #let _MAX_H = 3.4 #let _ASPECT_WIDE = 2.2 #let _UPSCALE_MAX = 1.15 #let stdfig(body) = context { let m = measure(body) let w = calc.max(m.width / 1in, 0.01) let h = calc.max(m.height / 1in, 0.01) let tw = if w / h > _ASPECT_WIDE { _WIDE_W } else { _STD_W } let s = calc.min(tw / w, _MAX_H / h, _UPSCALE_MAX) align(center, box(scale(x: s * 100%, y: s * 100%, reflow: true, body))) } #show figure: set block(breakable: false) #set figure(gap: 8pt) #show figure.caption: set text(size: 8.5pt, fill: rgb("#555")) == 2.2#h(0.6em)Type conversion === Learning objectives By the end of this section you should be able to - Explain how the interpreter uses implicit type conversion. - Use explicit type conversion with int(), float(), and str(). === Implicit type conversion Common operations update a variable such that the variable's data type needs to be changed. Ex: A GPS first assigns distance with 250, an integer. After a wrong turn, the GPS assigns distance with 252.5, a float. The Python interpreter uses #strong[implicit type conversion] to automatically convert one data type to another. Once distance is assigned with 252.5, the interpreter will convert distance from an integer to a float without the programmer needing to specify the conversion. #notebox("Note", rgb("#8a94a6"), rgb("#556666"), rgb("#f7f8fa"))[ #emph[Example: Book ratings] #link("https://www.openstax.org/r/book-ratings")[Example: Book ratings; ch 2, video 3] ] #notebox("Note", rgb("#8a94a6"), rgb("#556666"), rgb("#f7f8fa"))[ #emph[Implicit type conversion in practice] Consider the example above. ] === Explicit type conversion A programmer often needs to change data types to perform an operation. Ex: A program should read in two values using input() and sum the values. Remember input() reads in values as strings. A programmer can use #strong[explicit type conversion] to convert one data type to another. - #strong[int()] converts a data type to an integer. Any fractional part is removed. Ex: int(5.9) produces 5. - #strong[float()] converts a data type to a float. Ex: float(2) produces 2.0. - #strong[str()] converts a data type to a string. Ex: str(3.14) produces "3.14". #notebox("Note", rgb("#8a94a6"), rgb("#556666"), rgb("#f7f8fa"))[ #emph[Example: Ordering pizza] #link("https://www.openstax.org/r/ordering-pizza")[Example: Ordering pizza; ch 2, video 4] ] #notebox("Note", rgb("#8a94a6"), rgb("#556666"), rgb("#f7f8fa"))[ #emph[Example: Ordering pizza] Consider the example above. ] #notebox("Note", rgb("#8a94a6"), rgb("#556666"), rgb("#f7f8fa"))[ #emph[Using int(), float(), and str()] Given x = 4.5 and y = int(x), what is the value of each expression? ] #notebox("Note", rgb("#8a94a6"), rgb("#556666"), rgb("#f7f8fa"))[ #emph[Grade average] The following program computes the average of three predefined exam grades and prints the average twice. Improve the program to read the three grades from input and print the average first as a float, and then as an integer, using explicit type conversion. Ignore any differences that occur due to rounding. exam\_1 = 93.0 exam\_2 = 84.0 exam\_3 = 85.5 average = (exam\_1 + exam\_2 + exam\_3) / 3 print(average) print(average) ] #notebox("Note", rgb("#8a94a6"), rgb("#556666"), rgb("#f7f8fa"))[ #emph[Cups of water] The following program should read in the ounces of water the user drank today and compute the number of cups drank and the number of cups left to drink based on a daily goal. Assume a cup contains 8 ounces. Fix the code to calculate cups\_drank and cups\_left and match the following: - ounces is an integer representing the ounces the user drank. - cups\_drank is a float representing the number of cups of water drank. - cups\_left is an integer representing the number of cups of water left to drink (rounded down) out of the daily goal of 8 cups. ounces = input() print('Input ounces:', ounces, ', type:', type(ounces)) print(cups\_drank, 'cups drank, type:', type(cups\_drank)) print('About', cups\_left, 'cups left to drink, type:', type(cups\_left)) ] #notebox("Note", rgb("#8a94a6"), rgb("#556666"), rgb("#f7f8fa"))[ #emph[Product as float] The following program reads two integers in as strings. Calculate the product of the two integers, and print the result as a float. x = input("Enter the first integer: ") y = input("Enter the second integer: ") ]