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ikostan merged 2 commits into from
Oct 3, 2025
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[Sync Iteration] python/wordy/8 #189

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[Sync Iteration] python/wordy/8
exercism-solutions-syncer[bot] Oct 3, 2025
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Merge pull request #190 from ikostan/main
ikostan Oct 3, 2025
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99 changes: 99 additions & 0 deletions solutions/python/wordy/8/wordy.py
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"""
Parse and evaluate simple math word problems
returning the answer as an integer.

Handle a set of operations, in sequence.

Since these are verbal word problems, evaluate
the expression from left-to-right, ignoring the
typical order of operations.
"""

STR_TO_OPERATOR: dict[str, str] = {
"plus": "+",
"minus": "-",
"multiplied": "*",
"divided": "/",
}

REPLACEABLE: tuple = ("What", "is", "by")


def answer(question: str) -> int:
"""
Evaluate a simple word-based arithmetic question from left to right.

:param question: The input question, e.g., "What is 5 plus 13?"
:type question: str
:returns: The evaluated integer result.
:rtype: int
:raises ValueError: If the operation is unknown or the syntax is invalid.
"""
new_question: list[str] = [
word
for word in question.replace("?", "").split()
if word not in REPLACEABLE
]
# Reduce iteratively:
# evaluate the first three-token slice and fold the result left-to-right.
try:
result, new_question = int(new_question[0]), new_question[1:]
while new_question:
result, new_question = _math_operation(result, new_question)
except ValueError as exc:
if exc.args[0] == "unknown operation":
raise exc
raise ValueError("syntax error") from exc
except IndexError as exc:
raise ValueError("syntax error") from exc

return result


def _math_operation(result: int, question: list[str]) -> tuple[int, list[str]]:
"""
Compute a single binary arithmetic step for the current operator.

Expects the next tokens of the question to begin with the operator word
(e.g. ``plus``, ``minus``, ``multiplied``, ``divided``) followed by the
right-hand side operand. Division uses floor division (``//``) to comply
with the exercise rules.

:param result: Accumulated left-hand value computed so far.
:type result: int
:param question: Remaining tokens starting with the operator then rhs
integer, e.g. ``['plus', '4', ...]``.
:type question: list[str]
:returns: A tuple of the new accumulated result and the remaining tokens
after consuming the operator and rhs.
:rtype: tuple[int, list[str]]
:raises ValueError: If the operator is unknown or the token sequence is
malformed.
"""
math_operator: str = question[0]
# if the question contains an unknown operation.
if (
math_operator not in STR_TO_OPERATOR
and not math_operator.isdigit()
):
raise ValueError("unknown operation")
# if the question is malformed or invalid.
if math_operator.isdigit():
raise ValueError("syntax error")
# if the question is malformed or invalid.
if math_operator in STR_TO_OPERATOR and len(question) == 1:
raise ValueError("syntax error")

if STR_TO_OPERATOR[math_operator] == "+":
result += int(question[1])

if STR_TO_OPERATOR[math_operator] == "-":
result -= int(question[1])

if STR_TO_OPERATOR[math_operator] == "/":
result //= int(question[1])

if STR_TO_OPERATOR[math_operator] == "*":
result *= int(question[1])

return result, question[2:]