A simple Python class

We now define the Customer class described in class diagram below: an instance of this class will become the customer attribute of the BankAccount class.

Bank account classes

Note that it was possible to instantiate a BankAccount object by passing a string literal as customer. This is a consequence of Python's dynamic typing: no check is automatically made that the object passed as an argument to the class constructor is of any particular type.

The following code defines a Customer class and should be saved to a file called customer.py:

from datetime import datetime
class Customer:
    """ A class representing a bank customer. """

    def __init__(self, name, address, date_of_birth):
        self.name = name
        self.address = address
        self.date_of_birth = datetime.strptime(date_of_birth, '%Y-%m-%d')
        self.password = '1234'

    def get_age(self):
        """ Calculates and returns the customer's age. """
        today = datetime.today()
            birthday = self.date_of_birth.replace(year=today.year)
        except ValueError:
            # birthday is 29 Feb but today's year is not a leap year
            birthday = self.date_of_birth.replace(year=today.year,
                                               day=self.date_of_birth.day - 1)
        if birthday > today:
            return today.year - self.date_of_birth.year - 1
        return today.year - self.date_of_birth.year

Then we can pass Customer objects to our BankAccount constructor:

>>> from bank_account import BankAccount
>>> from customer import Customer
>>> customer1 = Customer('Helen Smith', '76 The Warren, Blandings, Sussex',
>>> account1 = BankAccount(customer1, 21457288, 1000)
>>> account1.customer.get_age()
>>> print(account1.customer.address)
76 The Warren, Blandings, Sussex