bank.py

"""
File: bank.py
Programming Exercise 10.3
The str for Bank returns a string of accounts sorted by name.
"""
import pickle
import random
from savingsaccount import SavingsAccount

class Bank:
    """This class represents a bank as a collection of savings accounts.
    An optional file name is also associated
    with the bank, to allow transfer of accounts to and
    from permanent file storage."""

    # The state of the bank is a dictionary of accounts and
    # a file name.  If the file name is None, a file name
    # for the bank has not yet been established.

    def __init__(self, fileName = None):
        """Creates a new dictionary to hold the accounts.
        If a file name is provided, loads the accounts from
        a file of pickled accounts."""
        self.accounts = {}
        self.fileName = fileName
        if fileName != None:
            fileObj = open(fileName, 'rb')
            while True:
                try:
                    account = pickle.load(fileObj)
                    self.add(account)
                except Exception:
                    fileObj.close()
                    break

    def __str__(self):
        """Returns the string representation of the bank."""
        #sorted(self.accounts)
        return "\n".join(map(str, sorted(self.accounts.values())))

    def makeKey(self, name, pin):
        """Returns a key for the account."""
        return name + "/" + pin

    def add(self, account):
        """Adds the account to the bank."""
        key = self.makeKey(account.getName(), account.getPin())
        self.accounts[key] = account

    def remove(self, name, pin):
        """Removes the account from the bank and
        and returns it, or None if the account does
        not exist."""
        key = self.makeKey(name, pin)
        return self.accounts.pop(key, None)

    def get(self, name, pin):
        """Returns the account from the bank,
        or returns None if the account does
        not exist."""
        key = self.makeKey(name, pin)
        return self.accounts.get(key, None)

    def computeInterest(self):
        """Computes and returns the interest on
        all accounts."""
        total = 0
        for account in self._accounts.values():
            total += account.computeInterest()
        return total

    def getKeys(self):
        """Returns a sorted list of keys."""
        # Exercise
        return []

    def save(self, fileName = None):
        """Saves pickled accounts to a file.  The parameter
        allows the user to change file names."""
        if fileName != None:
            self.fileName = fileName
        elif self.fileName == None:
            return
        fileObj = open(self.fileName, 'wb')
        for account in self.accounts.values():
            pickle.dump(account, fileObj)
        fileObj.close()

# Functions for testing
def createBank(numAccounts = 1):
    """Returns a new bank with the given number of 
    accounts."""
    names = ("Brandon", "Molly", "Elena", "Mark", "Tricia",
             "Ken", "Jill", "Jack")
    bank = Bank()
    upperPin = numAccounts + 1000
    for pinNumber in range(1000, upperPin):
        name = random.choice(names)
        balance = float(random.randint(100, 1000))
        bank.add(SavingsAccount(name, str(pinNumber), balance))
    return bank

def testBank(number = 0):
    """Returns a bank with the specified number of accounts and/or
    the accounts loaded from the specified file name."""
    bank = Bank()
    for i in range(number):
        bank.add(SavingsAccount('Name' + str(i + 1),
                                str(1000 + i),
                                100.00))
    return bank

def main(number = 10, fileName = None):
    """Creates and prints a bank, either from
    the optional file name argument or from the optional
    number."""
    bank = testBank(9)
    print(bank)

if __name__ == "__main__":
    main()