class Holding:

def __init__(self, name, shares, price, date):

self.name = name

self.shares = shares

self.price = price

self.date = date

def cost(self):

return self.price * self.shares

def sell(self, nshares):

self.shares -= nshares

@classmethod

def print_table(cls, objects, col_names):

print(f'Found {len(objects)} records')

for col_name in col_names:

print('{:>10s}'.format(col_name), end=' ')

print()

for obj in objects:

for col_name in col_names:

print('{:>10s}'.format(str(getattr(obj, col_name))), end=' ')

print()

class Portfolio:

def __init__(self):

self.holdings = []

@classmethod

def load(cls):

self = cls()

self.holdings.append(Holding('AA', 23, 45.6, '2023-07-08'))

self.holdings.append(Holding('IBM', 75, 34.6, '2023-06-08'))

self.holdings.append(Holding('IBM', 15, 300.6, '2023-05-01'))

self.holdings.append(Holding('MSFT', 15, 151.6, '2023-07-08'))

return self

def __iter__(self):

return self.holdings.__iter__()

def __len__(self):

return self.holdings.__len__()

def __getattr__(self, item):

# holdings.append and list related function exposed

return getattr(self.holdings, item)

if __name__ == '__main__':

h = Holding('AA', 23, 45.6, '2023-07-08')

print('Class attribute read h.name ', h.name)

h.name = 'Modified'

print('Class attribute set h.name ', h.name)

# del h.name

# AttributeError: 'Holding' object has no attribute 'name'

# print('Class attribute delete h.name ', h.name)

holdings = Portfolio.load()

print(holdings.append)

Holding.print_table(holdings, ['name', 'price'])