from dataclasses import dataclass, field
from datetime import datetime
from decimal import Decimal
from typing import Optional
@dataclass(frozen=True, slots=True, kw_only=True)
class MpesaTransactionRecord:
transaction_id: str
phone_number: str
amount: Decimal
account_reference: str
timestamp: datetime = field(default_factory=datetime.utcnow)
status: str = 'COMPLETED'
failure_reason: Optional[str] = None
def __post_init__(self) -> None:
if self.amount <= Decimal('0'):
raise ValueError(f'Amount must be positive, got {self.amount}')
if not self.phone_number.startswith('254') or len(self.phone_number) != 12:
raise ValueError(f'Invalid Kenyan MSISDN: {self.phone_number}')Replacing Plain Dictionaries with Type-Safe Python Dataclasses
Relying on loose dictionaries across Python applications causes runtime KeyError exceptions. Python's built-in dataclasses module provides an elegant, memory-efficient domain model structure.
frozen=True: Guarantees immutability and thread safety.slots=True: Dramatically reduces memory overhead in high-throughput loops.__post_init__: Enforces business domain validation on instantiation.
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