I use two classes to track accounts and transactions: class acct(object): # bank and brokerage account allacct = [] def __init__(self, name, bal

I use two classes to track accounts and transactions: class acct(object): # bank and brokerage account allacct = [] def __init__(self, name, balance, holdings=None): self.name = name self.balance = balance self.holdings = holdings self.xferamt = 0 self.accum = 0 # used to track cumulation ad hoc values acct.allacct.append(self) def buy(self, sec, amt, cost, day): rec = trans(('buy', sec, amt), -cost, day, self) self.balance -= cost if not self.holdings.has_key(sec): self.holdings[sec] = [0] self.holdings[sec][0] += amt self.holdings[sec].append(rec) ...... class trans(object): # transaction record object track cash invovled in each transaction allrec = [] def __init__(self, t, amt, day, where): try: self.type = t self.amt = amt self.date = date(year, month, day) self.where = where trans.allrec.append(self) except Exception as err: print t, amt, year, month, day, where raise err Then for each data line I just do any of the following: SOMEACCT.buy(...) SOMEACCT.sell(...) SOMEACCT.credit(...) SOMEACCT.debit(...) SOMEACCT.xfer(...) # classified by tax categories: SOMEACCT.int(...) SOMEACCT.div(...) SOMEACCT.fdiv(...) SOMEACCT.mint(...) SOMEACCT.mdiv(...) Then it is easy to query and do computations in any way one cares to write a function to do.