#set document(title: "13.4 Hierarchical inheritance", 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")) == 13.4#h(0.6em)Hierarchical inheritance === Learning objectives By the end of this section you should be able to - Label relationships between classes as types of inheritance. - Construct classes that form hierarchical inheritance. === Hierarchical inheritance basics #strong[Hierarchical inheritance] is a type of inheritance in which multiple classes inherit from a single superclass. #strong[Multilevel inheritance] is a type of inheritance in which a subclass becomes the superclass for another class. Combining hierarchical and multilevel inheritance creates a tree-like organization of classes. #notebox("Note", rgb("#8a94a6"), rgb("#556666"), rgb("#f7f8fa"))[ #emph[Hierarchical organization and types of inheritance] #link("https://www.openstax.org/r/inheritance-types")[Hierarchial organization and types of inheritance; ch 13, video 7] ] #notebox("Note", rgb("#8a94a6"), rgb("#556666"), rgb("#f7f8fa"))[ #emph[Hierarchical organization] ] === Implementing hierarchical inheritance Multiple classes can inherit from a single class by simply including the superclass name in each subclass definition. #examplebox("Example 1")[Choir members][ class ChoirMember:   def display(self):     print("Current choir member") class Soprano(ChoirMember):   def display(self):     super().display()     print("Part: Soprano") class Soprano1(Soprano):   def display(self):     super().display()     print("Division: Soprano 1") class Alto(ChoirMember):   def display(self):     super().display()     print("Part: Alto") class Tenor(ChoirMember):   def display(self):     super().display()     print("Part: Tenor") class Bass(ChoirMember):   def display(self):     super().display()     print("Part: Bass") mem\_10 = Alto() mem\_13 = Tenor() mem\_15 = Soprano1() mem\_10.display() print() mem\_13.display() print() mem\_15.display() The code's output is: Current choir member Part: Alto Current choir member Part: Tenor Current choir member Part: Soprano Division: Soprano 1 ] #notebox("Note", rgb("#8a94a6"), rgb("#556666"), rgb("#f7f8fa"))[ #emph[Implementing hierarchical inheritance] Consider the program: class A:   def \_\_init\_\_(self, a\_attr=0):     self.a\_attr = a\_attr class B(A):   def \_\_init\_\_(self, a\_attr=0, b\_attr=0):     super().\_\_init\_\_(a\_attr)     self.b\_attr = b\_attr class C(A):   def \_\_init\_\_(self, a\_attr=0, c\_attr=0):     super().\_\_init\_\_(a\_attr)     self.c\_attr = c\_attr class D(B):   def \_\_init\_\_(self, a\_attr=0, b\_attr=0, d\_attr=0):     super().\_\_init\_\_(a\_attr, b\_attr)     self.d\_attr = d\_attr b\_inst = B(2) c\_inst = C(c\_attr=4) d\_inst = D(6, 7) ] #notebox("Note", rgb("#8a94a6"), rgb("#556666"), rgb("#f7f8fa"))[ #emph[Overriding methods] Define three classes: Instrument, Woodwind, and String. - Instrument has instance attribute owner, with default value of "unknown". - Woodwind inherits from Instrument and has instance attribute material with default value of "wood". - String inherits from Instrument and has instance attribute num\_strings, with default value of 4. The output should match: This flute belongs to unknown and is made of silver This cello belongs to Bea and has 4 strings \# Define Instrument class \# Define Woodwind class \# Define String class print(f"This flute belongs to {flute\_1.owner} and is made of {flute\_1.material}") print(f"This cello belongs to {cello\_1.owner} and has {cello\_1.num\_strings} strings") ]