What patterns are suitable for data validation, object creation, and payment method selection?

To solve data validation, object creation, and payment method selection tasks, the following design patterns are often used:

1. Data Validation — Chain of Responsibility Pattern Allows sequential application of a set of validators, each checking a specific condition and passing control further if everything is in order.

2. Object Creation — Builder Pattern Suitable for step-by-step creation of complex objects with many parameters, ensuring readability and flexibility.

3. Payment Method Selection — Strategy Pattern Encapsulates various payment algorithms and allows choosing the appropriate one depending on conditions (e.g., card type, region, currency).

Example pseudocode for selecting a payment method:

class PaymentStrategy:
    def pay(self, amount):
        pass

class CreditCardPayment(PaymentStrategy):
    def pay(self, amount):
        # card payment logic
        pass

class PayPalPayment(PaymentStrategy):
    def pay(self, amount):
        # PayPal payment logic
        pass

class PaymentContext:
    def __init__(self, strategy: PaymentStrategy):
        self.strategy = strategy

    def execute_payment(self, amount):
        self.strategy.pay(amount)

# Usage
payment_method = CreditCardPayment()  # strategy selection
context = PaymentContext(payment_method)
context.execute_payment(100)

This approach facilitates maintenance and extension of functionality.