Something like this...

financial_common.py

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+from datetime import datetime
+from dateutil.relativedelta import relativedelta
+
+DATE = 'Date'
+ASSETS = 'Assets'
+LIABILITIES = 'Liabilities'
+CAPITAL = 'Capital'
+DUES = 'Dues'
+DONATIONS = 'Donations'
+FOOD_DONATIONS =  'Food donations'
+MEMBERS = 'Members'
+DONATING_MEMBERS = 'Donating members'
+EXPENSES = 'Expenses'
+FOOD_EXPENSES = 'Food expenses'
+PROJECTED_CAPITAL = 'Projected capital'
+PROJECTED_DUES = 'Projected dues'
+PROJECTED_DONATIONS = 'Projected donations'
+PROJECTED_MEMBERS = 'Projected members'
+PROJECTED_DONATING_MEMBERS = 'Projected donating members'
+PROJECTED_FOOD_DONATIONS = 'Projected food donations'
+PROJECTED_FOOD_EXPENSES = 'Projected food expenses'
+CAPITAL_TARGET = 'Target balance (3 month buffer)'
+
+MONTH_START_DAY = 4
+
+def figure_out_today_and_start_and_end_dates():
+    today = datetime.now().replace(second=0, microsecond=0)
+    if today.day < MONTH_START_DAY:
+        today -= relativedelta(months=+1)
+    delta = relativedelta(months=+6)
+    start = today - delta
+    end = today + delta
+
+    return [start, today, end]
+
+def report_days(start_date, end_date):
+    delta = relativedelta(months=+1)
+    d = start_date.replace(day=MONTH_START_DAY)
+    while d < end_date.replace(day=MONTH_START_DAY):
+        d += delta
+        yield d

financial_csv.py

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+import csv
+
+import financial_common
+
+def write_to_csv_the(financial_records):
+    fieldnames = [
+        DATE,
+        ASSETS,
+        LIABILITIES,
+        CAPITAL,
+        PROJECTED_CAPITAL,
+        DUES,
+        PROJECTED_DUES,
+        DONATIONS,
+        PROJECTED_DONATIONS,
+        MEMBERS,
+        PROJECTED_MEMBERS,
+        DONATING_MEMBERS,
+        PROJECTED_DONATING_MEMBERS,
+        EXPENSES,
+        FOOD_DONATIONS,
+        PROJECTED_FOOD_DONATIONS,
+        FOOD_EXPENSES,
+        PROJECTED_FOOD_EXPENSES,
+        CAPITAL_TARGET,
+    ]
+
+    with open('foobar.csv', 'wb') as csvfile:
+        writer = csv.DictWriter(csvfile, delimiter=',', quotechar='"', quoting=csv.QUOTE_MINIMAL, fieldnames=fieldnames)
+
+        writer.writeheader()
+        for finances_for_a_month in financial_records:
+            writer.writerow(finances_for_a_month)

financial_future.py

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+from __future__ import print_function
+from datetime import datetime
+
+import financial_common
+
+def get_future_projections_based_on( historical_records ):
+    future_projections = []
+
+    monthly_amount_projections = get_monthly_amount_projections_based_on( historical_records )
+
+    for month in months_to_project():
+        starting_capital = future_projections[-1][PROJECTED_CAPITAL] if len(future_projections) else historical_records[-1][CAPITAL]
+
+        future_projections.append( project_finances_for( month, starting_capital, finances_for_current_month, monthly_amount_projections ) )
+
+    return future_projections
+
+def months_to_project():
+    start, today, end = figure_out_today_and_start_and_end_dates()
+    return report_days(today, end)
+
+def project_finances_for( month, starting_capital, finances_for_current_month, monthly_amount_projections ):
+    print(month)
+
+    return {
+        # same for each projected month
+        DATE: month,
+        PROJECTED_DUES: finances_for_current_month[DUES],
+        PROJECTED_DONATIONS: finances_for_current_month[DONATIONS],
+        PROJECTED_MEMBERS: finances_for_current_month[MEMBERS],
+        PROJECTED_DONATING_MEMBERS: finances_for_current_month[DONATING_MEMBERS],
+        PROJECTED_FOOD_DONATIONS: monthly_amount_projections[ 'food income' ],
+        PROJECTED_FOOD_EXPENSES: monthly_amount_projections[ 'food expenses' ],
+
+        # differs in each month
+        PROJECTED_CAPITAL: starting_capital + monthly_amount_projections['income'] + monthly_amount_projections['expenses'],
+
+        # two different values - before & after rent increase
+        CAPITAL_TARGET: (monthly_amount_projections['expenses'] - rent_increase_for( month )) * -3,
+    }
+
+def get_monthly_amount_projections_based_on( historical_records ):
+    current_month_amounts = historical_records[-1]
+
+    monthly_amount_projections['income'] = current_month_amounts[DUES] + current_month_amounts[DONATIONS]
+    monthly_amount_projections['expenses'] = get_average( EXPENSES, historical_records )
+    monthly_amount_projections['food income'] = get_average( FOOD_DONATIONS, historical_records )
+    monthly_amount_projections['food expenses'] = get_average( FOOD_EXPENSES, historical_records )
+
+    print( "Projected income: ", monthly_amount_projections['income'] )
+    print( "Projected expenses: ", monthly_amount_projections['expenses'] )
+
+    return monthly_amount_projections
+
+def rent_increase_for( month ):
+    february_2015 = datetime(2015, 02, 01):
+
+    if month >= february_2015
+        rent_increase = 100
+    else
+        rent_increase = 0
+
+    return rent_increase
+
+def get_average( datum_key, financial_records ):
+    total = sum( record[datum_key] for record in financial_records )
+
+    return total / len( financial_records )

financial_history.py

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+import calendar
+import gnucashxml
+import sys
+from datetime import datetime
+from __future__ import print_function
+
+import financial_common
+
+def get_historical_records():
+    historical_records = []
+
+    book = get_requested_financial_book()
+
+    for month in months_to_report_on():
+        historical_records.append( book.finances_for( month ) )
+
+    return historical_records
+
+def get_requested_financial_book():
+    provided_by_user = sys.argv[1]
+    return Book( gnucash_filename = provided_by_user )
+
+def months_to_report_on():
+    start, today, end = figure_out_today_and_start_and_end_dates()
+    return report_days( start, today )
+
+class Book:
+    def __init__( self, gnucash_filename ):
+        self.book = gnucashxml.from_filename( gnucash_filename )
+
+    def finances_for( self, month, book ):
+        assets = self.get_assets_on( date = month )
+        liabilities = self.get_liability_on( date = month )
+        expenses = self.get_expenses_for( month )
+
+        monthly_finances = {
+            DATE: month,
+            ASSETS: assets,
+            LIABILITIES: liabilities,
+            CAPITAL: assets + liabilities,
+            DUES: self.get_amount_of( "Member Dues", month ),
+            DONATIONS: self.get_amount_of( "Regular donations", month ),
+            FOOD_DONATIONS: self.get_amount_of( "Food and Drink Donations", month ),
+            MEMBERS: self.get_number_of( "Member Dues", month ),
+            DONATING_MEMBERS: self.get_number_of( "Regular donations", month ),
+            EXPENSES: expenses,
+            FOOD_EXPENSES: self.get_amount_of( "Groceries", month ),
+            CAPITAL_TARGET: expenses * -3,
+        }
+
+        display( monthly_finances )
+
+        return monthly_finances
+
+    def get_assets_on( self, date ):
+        assets = self.book.find_account("Current Assets")
+
+        asset_total = 0
+        for account in assets.children:
+            if account.name != "Prepaid Rent":
+                asset_total += sum(split.value for split in account.splits if split.transaction.date.replace(tzinfo=None) <= date)
+
+        return asset_total
+
+    def get_liability_on( self, date ):
+        liability = self.get_total( "Active Members", date ) + self.get_total( "Former Members", date )
+
+        return liability
+
+    def get_total( self, account_name, date ):
+        account = self.book.find_account( account_name )
+        total = sum( split.value for split in account.get_all_splits() if split.transaction.date.replace(tzinfo=None) <= date)
+
+        return total
+
+    def get_expenses_for( self, month_end ):
+        end_date = month_end
+        start_date = subtract_month(month_end)
+
+        expense_accounts = self.book.find_account("Expenses")
+        expenses = 0
+        for account in expense_accounts.children:
+            if account.name != "Anti-social 10-04" and account.name != "Groceries":
+                for split in account.splits:
+                    if start_date < split.transaction.date.replace(tzinfo=None) <= end_date:
+                        expenses += split.value
+
+                for subaccount in account.children:
+                    for split in subaccount.splits:
+                        if start_date < split.transaction.date.replace(tzinfo=None) <= end_date:
+                            expenses += split.value
+
+
+        return expenses * -1
+
+    def get_number_of( self, account_name, month_end ):
+        return sum( len( entry.transaction.splits ) - 1 for entry in self.get_entries_for( account_name, month_end ) )
+
+    def get_amount_of( self, account_name, month_end ):
+        return sum( entry.value for entry in self.get_entries_for( account_name, month_end ) ) * -1
+
+    def get_entries_for( self, account_name, month_end ):
+        end_date = month_end
+        start_date = subtract_month(month_end)
+
+        account = self.book.find_account( account_name )
+
+        entries = []
+
+        for split in account.get_all_splits():
+            if start_date < split.transaction.date.replace(tzinfo=None) <= end_date:
+                entries.add( split )
+
+        return entries
+
+def subtract_month(date):
+    month = date.month - 2
+    month = month % 12 + 1
+    year = date.year - 1/12
+    day = min(date.day, calendar.monthrange(year, month)[1])
+    return datetime(year, month, day)
+
+def display( monthly_finances ):
+    print(monthly_finances[ DATE ])
+    print("Total assets: ", monthly_finances[ ASSETS ])
+    print("Total liability: ", monthly_finances[ LIABILITIES ])
+    print("Available capital: ", monthly_finances[ CAPITAL ])
+    print("Dues collected last month: ", monthly_finances[ DUES ])
+    print("Dues paying members: ", monthly_finances[ MEMBERS ])
+    print("Regular donations collected last month: ", monthly_finances[ DONATIONS ])
+    print("Regularly donating members: ", monthly_finances[ DONATING_MEMBERS ])
+    print("Food donations: ", monthly_finances[ FOOD_DONATIONS ])
+    print("Total expected income: ", (monthly_finances[ DUES ] + monthly_finances[ DONATIONS ] + monthly_finances[ FOOD_DONATIONS ]))
+    print("Expenses: ", monthly_finances[ EXPENSES ])
+    print("Food expenses: ", monthly_finances[ FOOD_EXPENSES ])
+    print()