Turn a problem into a thin Python product

Describe the job

Write: When this situation happens, this user needs to achieve this result, so they can get this benefit. Avoid naming your solution in the problem statement.

Draw the one path

For an invoice reminder tool, the thin path might be upload CSV, validate rows, generate reminders, review, and export. Authentication dashboards and team permissions can wait.

Choose failure behavior

Define what happens with missing data, duplicate records, network errors, and retries. Reliability is part of scope.

Measure the outcome

Pick one activation event that proves the user reached value. Product analytics should answer a decision, not merely collect events.

Working example

from dataclasses import dataclass

@dataclass(frozen=True)
class Reminder:
    customer: str
    email: str
    amount_cents: int

def create_reminder(row: dict[str, str]) -> Reminder:
    amount = int(row["amount_cents"])
    if amount <= 0:
        raise ValueError("amount must be positive")
    email = row["email"].strip().lower()
    if "@" not in email:
        raise ValueError("email is invalid")
    return Reminder(row["customer"].strip(), email, amount)