Goals and entries

Specify inherited state, operands, failures and effects before implementation. Verify a real file project rather than treating a single code block as module organization.

HW4 covers weeks10–12. Solo2 covers10/11 and uses its configured deadline after week11. Neither gets a new “this Sunday” date here.

Staff points are not automatically awarded by code tests. C is required practice without extra weight; raw scores do not change course weights.

Entries are standalone, annotated interfaces. Self needs no separate annotation. Do not use input or rely on a preceding slide. Unspecified object types need no automatic conversion; numerical tests use moderate magnitudes.

Part A · Classes and protocols

10-1 Shape family

class Shape:
    def area(self) -> float: ...
    def name(self) -> str: ...
class Circle(Shape):
    def __init__(self, r: float) -> None: ...
class Rectangle(Shape):
    def __init__(self, w: float, h: float) -> None: ...
class Triangle(Shape):
    def __init__(self, a: float, b: float, c: float) -> None: ...
def total_area(shapes: list[Shape]) -> float: ...

Shape can be constructed; its area raises NotImplementedError. Name reports the actual class name. Dimensions are finite and positive; triangles satisfy strict inequalities. Invalid construction raises ValueError. Use math.pi and Heron’s formula. Empty total_area returns0; neither the list nor objects are changed.

Circle(1) has areaπ; Rectangle(2,3) and Triangle(3,4,5) have area6. Reject Triangle(1,1,3). Explain the degeneracy rejection, rather than selecting a different None/error policy. Code: w10-shapes,4 automatic.

10-2 Account inheritance

Submit all three definitions, not subclasses assuming L09 was run first.

class BankAccount:
    def __init__(self, owner: str, balance: int = 0) -> None: ...
    def deposit(self, amount: int) -> None: ...
    def withdraw(self, amount: int) -> bool: ...
    def statement(self) -> str: ...
class SavingsAccount(BankAccount):
    def __init__(self, owner: str, balance: int = 0,
                 interest_rate: float = 0.0) -> None: ...
    def add_interest(self) -> None: ...
class CheckingAccount(BankAccount):
    def __init__(self, owner: str, balance: int = 0,
                 overdraft_limit: int = 0) -> None: ...

Money uses integer cents. Public owner/balance/history follow L09. A nonnegative integer starting balance is required, otherwise ValueError. Nonpositive/noninteger deposit and withdrawal amounts are rejected: deposit returns None, withdrawal False, with unchanged state. Accepted history entries are (“deposit”,amount) or (“withdraw”,amount) using ordinary ASCII string quotes in code. Statement starts owner: balance cents, followed by action: amount cents, newline-joined without a trailing newline.

Both subclass initializers use super. Savings takes a finite rate0≤rate≤1; invalid rates raise ValueError. Quantize Decimal(str(rate))×balance to integer cents using ROUND_HALF_UP. Positive interest adds (“interest”,cents), zero adds no history, and add_interest returns None. This is an educational rounding contract, not a financial production system.

Checking starts nonnegative but supports later balances down to−overdraft_limit. The limit is a nonnegative integer. Overridden withdrawal rejects a value below that bound without changing history/balance. The base’s nonnegative-balance guarantee is not a universal family contract. Discuss whether directly calling base withdrawal meets this policy.

Code: w10-accounts,4 automatic.

10-3 Money

class Money:
    def __init__(self, yuan: float) -> None: ...
    def __repr__(self) -> str: ...
    def __add__(self, other: "Money") -> "Money": ...
    def __sub__(self, other: "Money") -> "Money": ...
    def __eq__(self, other: object) -> bool: ...
    def __lt__(self, other: "Money") -> bool: ...

Accept finite int/float yuan with magnitude≤10^9; otherwise ValueError. Store integer cents. Convert str(value) to Decimal, multiply by100 and quantize using ROUND_HALF_UP:1.005→101 cents,−1.005→−101. This operates on the supplied value’s decimal display, not an imagined original decimal intent. Read the decimal interface first; int(float*100) truncation is not this contract.

Repr has exactly two decimals, including Money(12.50), Money(-1.01), Money(0.00). Addition/subtraction return new objects and preserve inputs; comparisons use cents. Unsupported operand methods return NotImplemented. Equality to an unrelated object is False; unsupported arithmetic/ordering generally raises TypeError. Results may exceed the constructor-input bound without passing through float storage.

Check Money(0.1)+Money(0.2)==Money(0.3), sorting, negatives, ties and input preservation. Code: w10-money,4 automatic.

10-4 Deck

class Deck:
    def __init__(self) -> None: ...
    def __len__(self) -> int: ...
    def __getitem__(self, i: int) -> str: ...
    def __contains__(self, card: str) -> bool: ...
    def shuffle(self) -> None: ...
    def deal(self, n: int) -> list[str]: ...

Use ASCII rank+suit. Suits are C/D/H/S; ranks are A/2/…/10/J/Q/K. Initial ordering groups by suit then rank: AC at0, KC at12, AD at13, KS last. There are52 unique cards, no jokers, and independent decks.

Length reports remaining cards. Integer positive/negative indexing works; invalid indices raise IndexError. Membership returns bool. Sequence-style iteration must stop at an invalid index, not return None forever.

Deal takes n cards from the front, removes them and returns a new list. n is a nonnegative integer no larger than the remainder; invalid values raise ValueError without mutation. Zero deals nothing. Shuffle mutates and returns None while retaining length and card multiplicities. No particular shuffled sequence or mandatory change on every call is required; do not reseed internally to fake randomness.

Code: w10-deck,4 automatic.

A design record

w10-a-notes: four staff responses worth2 each: shape rejection/polymorphism; account and overdraft contracts/super; Money rounding/sentinel/preservation; Deck representation, edges and isolation. A separate zero-point declaration records actual assistance.

Part B · Real module organization

10-5 Separate modules and imports

Use five files, fixing the old “three files” count:

shapes.py   # shapes
accounts.py # accounts
money.py    # money
cards.py    # deck
main.py     # entry

Each business module starts with a docstring and has a main guard. Direct execution prints one recognizable self-test line: SELFTEST shapes/accounts/money/cards. Importing it prints nothing. Main imports all four, demonstrates at least one object from each, exits successfully and prints a result without SELFTEST. Main also has a docstring/guard; importing it does not run the demo.

The existing single-source submission entry takes project_files() -> dict[str,str], returning exactly these five filenames and their complete sources. The evaluator writes only these names into its own temporary sandbox and runs/imports there; it does not accept arbitrary absolute paths or add a zip-upload feature. Project_files must not run the project, read local files or install dependencies.

Keep the real five-file project locally. The adapter packages its sources rather than replacing module work. Business interfaces must support normal Part A examples; no input, network or GUI dependency. Use only the standard library and these files.

w10-module-project:8 automatic. w10-b-notes:2 staff for responsibilities/separating Money,2 for actual direct-run/import evidence; declaration0. A guard’s textual presence is not evidence that imports behave correctly.

Part C · Environment and debugging

w10-c-tools,0 points. Record interpreter, matching pip, module source and environment. Observe a main guard or name shadow in an independent temporary folder, then remove your example. Do not leave random.py in a real project or uninstall another person’s dependencies.

Identify self, the current class and MRO rather than defining super as always the direct parent. State limitations instead of fabricating outputs/screenshots. C adds no weight.

4. Solo assignment2: counting primes five ways

Solo2 opens in week10 and covers10/11, worth5%; three solo assignments total15%. Its configured calendar determines the deadline. It is not the old7.5% big-integer project.

Count primes 0≤p<n for0≤n≤100000. Values≤2 return0; negative n raises ValueError. Larger inputs are not required. Examples: n=0/2→0, n=3→1, n=10→4. Return an integer without printing.

MR handles values below2,2/3 and other even values before bases2,3 on remaining odds. The known deterministic bound below1,373,653 covers candidates below100000. This is not a determinism claim for arbitrary integers. L11 and assignment material develop decomposition/modular exponentiation and the other algorithms; establish interfaces and evidence now rather than requiring untaught implementations immediately.

Each method entry carries16 automatic raw points. The staff report carries20;100 raw points normalize to this assignment’s5%. Tests primarily check results/edges; staff inspect sources and records for genuinely different methods. Do not wrap one algorithm five times. Each entry includes its helpers; pow(a,d,m) is allowed for MR.

w10-primes-report: method/source evidence6, boundary/cross-checking6, fair reproducible timing6, conclusions/limits2, declaration0. Verify correctness before timing. Slow methods may use smaller n rather than another algorithm. Record actual sizes, repetitions, environment, preparation/query accounting and counts; make at least three measurements, without claiming a single ratio is universal.

5. Later reference: big integers

BigInt starts in week12, not as a current7.5% deliverable. Keep decimal strings, sign/grouped-digit representation, str/repr/eq/lt/add/sub/mul and the prohibition on converting complete operands to int as the implementation. Int remains a test oracle. Check zero, leading zeros, negatives, unequal lengths, negative differences and carry/borrow/multiplication. A one-page report covers representation, sign logic and boundary/random checks.

The old20/20/20/10/15/5/10 breakdown is historical, not the current rubric. Future requirements retain the calendar’s three5% assignments; knowledge is not removed.

Before submission

• Separate HW4 code/project/cards and match annotations, errors and results.
• Check independent instances, complete state after rejection, rounding/unsupported operands and finite Deck iteration.
• Verify module documentation, silent imports, direct self-tests and the real main demonstration.
• Match solo2’s counting interval, five genuine implementations, and correctness-before-timing evidence.
• Declare actual assistance/nonuse and unfinished steps; a locally saved project is not an online submission.